2d610c2300
First a few notes about Cogl coordinate systems: - Cogl defines the window origin, viewport origin and texture coordinates origin to be top left unlike OpenGL which defines them as bottom left. - Cogl defines the modelview and projection identity matrices in exactly the same way as OpenGL. - I.e. we believe that for 2D centric constructs: windows/framebuffers, viewports and textures developers are more used to dealing with a top left origin, but when modeling objects in 3D; an origin at the center with y going up is quite natural. The way Cogl handles textures is by uploading data upside down in OpenGL terms so that bottom left becomes top left. (Note: This also has the benefit that we don't need to flip the data we get from image decoding libraries since they typically also consider top left to be the image origin.) The viewport and window coords are mostly handled with various y = height - y tweaks before we pass y coordinates to OpenGL. Generally speaking though the handling of coordinate spaces in Cogl is a bit fragile. I guess partly because none of it was design to be, it just evolved from how Clutter defines its coordinates without much consideration or testing. I hope to improve this over a number of commits; starting here. This commit deals with the fact that offscreen draw buffers may be bound to textures but we don't "upload" the texture data upside down, and so if you texture from an offscreen draw buffer you need to manually flip the texture coordinates to get it the right way around. We now force offscreen rendering to be flipped upside down by tweaking the projection matrix right before we submit it to OpenGL to scale y by -1. The tweak is entirely hidden from the user such that if you call cogl_get_projection you will not see this scale.
456 lines
11 KiB
C
456 lines
11 KiB
C
/*
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* Cogl
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*
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* An object oriented GL/GLES Abstraction/Utility Layer
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*
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* Copyright (C) 2009 Intel Corporation.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 02111-1307, USA.
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*
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* Authors:
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* Havoc Pennington <hp@pobox.com> for litl
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* Robert Bragg <robert@linux.intel.com>
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*/
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include "cogl.h"
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#include "cogl-context.h"
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#include "cogl-internal.h"
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#include "cogl-matrix-stack.h"
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#include "cogl-draw-buffer-private.h"
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typedef struct {
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CoglMatrix matrix;
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gboolean is_identity;
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/* count of pushes with no changes; when a change is
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* requested, we create a new state and decrement this
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*/
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int push_count;
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} CoglMatrixState;
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/**
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* CoglMatrixStack:
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*
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* Stores a cogl-side matrix stack, which we use as a cache
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* so we can get the matrix efficiently when using indirect
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* rendering.
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*/
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struct _CoglMatrixStack
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{
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GSList *stack;
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/* which state does GL have, NULL if unknown */
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CoglMatrixState *flushed_state;
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gboolean flushed_identity;
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};
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/* XXX: this doesn't initialize the matrix! */
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static CoglMatrixState*
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_cogl_matrix_state_new (void)
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{
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CoglMatrixState *state;
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state = g_slice_new (CoglMatrixState);
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state->push_count = 0;
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state->is_identity = FALSE;
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return state;
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}
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static void
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_cogl_matrix_state_destroy (CoglMatrixState *state)
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{
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g_slice_free (CoglMatrixState, state);
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}
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static CoglMatrixState*
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_cogl_matrix_stack_top (CoglMatrixStack *stack)
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{
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return stack->stack->data;
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}
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/* XXX:
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* Operations like scale, translate, rotate etc need to have an
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* initialized state->matrix to work with, so they will pass
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* initialize = TRUE.
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*
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* _cogl_matrix_stack_load_identity and _cogl_matrix_stack_set on the
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* other hand don't so they will pass initialize = FALSE
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*
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* NB: Identity matrices are represented by setting
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* state->is_identity=TRUE in which case state->matrix will be
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* uninitialized.
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*/
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static CoglMatrixState *
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_cogl_matrix_stack_top_mutable (CoglMatrixStack *stack,
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gboolean initialize)
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{
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CoglMatrixState *state;
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CoglMatrixState *new_top;
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state = _cogl_matrix_stack_top (stack);
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if (state->push_count == 0)
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{
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if (state->is_identity && initialize)
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cogl_matrix_init_identity (&state->matrix);
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return state;
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}
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state->push_count -= 1;
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new_top = _cogl_matrix_state_new ();
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if (initialize)
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{
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if (state->is_identity)
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cogl_matrix_init_identity (&new_top->matrix);
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else
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new_top->matrix = state->matrix;
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if (stack->flushed_state == state)
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stack->flushed_state = new_top;
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}
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stack->stack = g_slist_prepend (stack->stack, new_top);
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return new_top;
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}
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CoglMatrixStack*
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_cogl_matrix_stack_new (void)
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{
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CoglMatrixStack *stack;
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CoglMatrixState *state;
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stack = g_slice_new0 (CoglMatrixStack);
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state = _cogl_matrix_state_new ();
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state->is_identity = TRUE;
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stack->stack = g_slist_prepend (stack->stack, state);
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return stack;
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}
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void
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_cogl_matrix_stack_destroy (CoglMatrixStack *stack)
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{
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while (stack->stack)
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{
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CoglMatrixState *state;
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state = stack->stack->data;
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_cogl_matrix_state_destroy (state);
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stack->stack =
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g_slist_delete_link (stack->stack,
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stack->stack);
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}
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g_slice_free (CoglMatrixStack, stack);
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}
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void
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_cogl_matrix_stack_push (CoglMatrixStack *stack)
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{
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CoglMatrixState *state;
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state = _cogl_matrix_stack_top (stack);
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/* we lazily create a new stack top if someone changes the matrix
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* while push_count > 0
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*/
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state->push_count += 1;
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}
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void
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_cogl_matrix_stack_pop (CoglMatrixStack *stack)
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{
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CoglMatrixState *state;
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state = _cogl_matrix_stack_top (stack);
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if (state->push_count > 0)
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{
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state->push_count -= 1;
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}
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else
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{
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if (stack->stack->next == NULL)
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{
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g_warning ("Too many matrix pops");
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return;
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}
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if (stack->flushed_state == state)
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{
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stack->flushed_state = NULL;
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}
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stack->stack =
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g_slist_delete_link (stack->stack,
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stack->stack);
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_cogl_matrix_state_destroy (state);
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}
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}
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void
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_cogl_matrix_stack_load_identity (CoglMatrixStack *stack)
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{
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CoglMatrixState *state;
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state = _cogl_matrix_stack_top_mutable (stack, FALSE);
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/* NB: Identity matrices are represented by setting
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* state->is_identity = TRUE and leaving state->matrix
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* uninitialized.
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*
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* This is done to optimize the heavy usage of
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* _cogl_matrix_stack_load_identity by the Cogl Journal.
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*/
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if (!state->is_identity)
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{
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state->is_identity = TRUE;
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/* mark dirty */
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stack->flushed_state = NULL;
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}
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}
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void
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_cogl_matrix_stack_scale (CoglMatrixStack *stack,
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float x,
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float y,
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float z)
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{
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CoglMatrixState *state;
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state = _cogl_matrix_stack_top_mutable (stack, TRUE);
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cogl_matrix_scale (&state->matrix, x, y, z);
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/* mark dirty */
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stack->flushed_state = NULL;
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state->is_identity = FALSE;
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}
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void
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_cogl_matrix_stack_translate (CoglMatrixStack *stack,
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float x,
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float y,
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float z)
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{
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CoglMatrixState *state;
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state = _cogl_matrix_stack_top_mutable (stack, TRUE);
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cogl_matrix_translate (&state->matrix, x, y, z);
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/* mark dirty */
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stack->flushed_state = NULL;
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state->is_identity = FALSE;
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}
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void
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_cogl_matrix_stack_rotate (CoglMatrixStack *stack,
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float angle,
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float x,
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float y,
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float z)
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{
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CoglMatrixState *state;
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state = _cogl_matrix_stack_top_mutable (stack, TRUE);
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cogl_matrix_rotate (&state->matrix, angle, x, y, z);
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/* mark dirty */
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stack->flushed_state = NULL;
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state->is_identity = FALSE;
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}
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void
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_cogl_matrix_stack_multiply (CoglMatrixStack *stack,
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const CoglMatrix *matrix)
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{
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CoglMatrixState *state;
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state = _cogl_matrix_stack_top_mutable (stack, TRUE);
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cogl_matrix_multiply (&state->matrix, &state->matrix, matrix);
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/* mark dirty */
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stack->flushed_state = NULL;
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state->is_identity = FALSE;
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}
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void
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_cogl_matrix_stack_frustum (CoglMatrixStack *stack,
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float left,
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float right,
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float bottom,
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float top,
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float z_near,
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float z_far)
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{
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CoglMatrixState *state;
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state = _cogl_matrix_stack_top_mutable (stack, TRUE);
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cogl_matrix_frustum (&state->matrix,
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left, right, bottom, top,
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z_near, z_far);
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/* mark dirty */
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stack->flushed_state = NULL;
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state->is_identity = FALSE;
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}
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void
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_cogl_matrix_stack_perspective (CoglMatrixStack *stack,
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float fov_y,
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float aspect,
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float z_near,
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float z_far)
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{
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CoglMatrixState *state;
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state = _cogl_matrix_stack_top_mutable (stack, TRUE);
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cogl_matrix_perspective (&state->matrix,
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fov_y, aspect, z_near, z_far);
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/* mark dirty */
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stack->flushed_state = NULL;
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state->is_identity = FALSE;
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}
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void
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_cogl_matrix_stack_ortho (CoglMatrixStack *stack,
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float left,
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float right,
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float bottom,
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float top,
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float z_near,
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float z_far)
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{
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CoglMatrixState *state;
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state = _cogl_matrix_stack_top_mutable (stack, TRUE);
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cogl_matrix_ortho (&state->matrix,
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left, right, bottom, top, z_near, z_far);
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/* mark dirty */
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stack->flushed_state = NULL;
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state->is_identity = FALSE;
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}
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void
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_cogl_matrix_stack_get (CoglMatrixStack *stack,
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CoglMatrix *matrix)
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{
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CoglMatrixState *state;
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state = _cogl_matrix_stack_top (stack);
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/* NB: identity matrices are lazily initialized because we can often avoid
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* initializing them at all if nothing is pushed on top of them since we
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* load them using glLoadIdentity()
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*
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* The Cogl journal typically loads an identiy matrix because it performs
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* software transformations, which is why we have optimized this case.
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*/
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if (state->is_identity)
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cogl_matrix_init_identity (matrix);
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else
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*matrix = state->matrix;
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}
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void
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_cogl_matrix_stack_set (CoglMatrixStack *stack,
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const CoglMatrix *matrix)
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{
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CoglMatrixState *state;
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state = _cogl_matrix_stack_top_mutable (stack, FALSE);
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state->matrix = *matrix;
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/* mark dirty */
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stack->flushed_state = NULL;
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state->is_identity = FALSE;
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}
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void
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_cogl_matrix_stack_flush_to_gl (CoglMatrixStack *stack,
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CoglMatrixMode mode)
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{
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CoglMatrixState *state;
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_COGL_GET_CONTEXT (ctx, NO_RETVAL);
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state = _cogl_matrix_stack_top (stack);
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if (stack->flushed_state == state)
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return;
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if (ctx->flushed_matrix_mode != mode)
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{
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GLenum gl_mode;
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switch (mode)
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{
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case COGL_MATRIX_MODELVIEW:
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gl_mode = GL_MODELVIEW;
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break;
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case COGL_MATRIX_PROJECTION:
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gl_mode = GL_PROJECTION;
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break;
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case COGL_MATRIX_TEXTURE:
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gl_mode = GL_TEXTURE;
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break;
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}
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GE (glMatrixMode (gl_mode));
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ctx->flushed_matrix_mode = mode;
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}
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/* Because Cogl defines texture coordinates to have a top left origin and
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* because offscreen draw buffers may be used for rendering to textures we
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* always render upside down to offscreen buffers.
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*/
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if (mode == COGL_MATRIX_PROJECTION &&
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cogl_is_offscreen (_cogl_get_draw_buffer ()))
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{
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CoglMatrix flipped_projection;
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CoglMatrix *projection =
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state->is_identity ? &ctx->identity_matrix : &state->matrix;
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cogl_matrix_multiply (&flipped_projection,
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&ctx->y_flip_matrix, projection);
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GE (glLoadMatrixf (cogl_matrix_get_array (&flipped_projection)));
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stack->flushed_identity = FALSE;
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}
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else
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{
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if (state->is_identity)
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{
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if (!stack->flushed_identity)
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GE (glLoadIdentity ());
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stack->flushed_identity = TRUE;
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}
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else
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{
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GE (glLoadMatrixf (cogl_matrix_get_array (&state->matrix)));
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stack->flushed_identity = FALSE;
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}
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}
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stack->flushed_state = state;
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}
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void
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_cogl_matrix_stack_dirty (CoglMatrixStack *stack)
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{
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stack->flushed_state = NULL;
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stack->flushed_identity = FALSE;
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}
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