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mutter-performance-source/cogl/cogl-pipeline-vertend-fixed.c
Robert Bragg e3d6bc36d3 Re-design the matrix stack using a graph of ops
This re-designs the matrix stack so we now keep track of each separate
operation such as rotating, scaling, translating and multiplying as
immutable, ref-counted nodes in a graph.

Being a "graph" here means that different transformations composed of
a sequence of linked operation nodes may share nodes.

The first node in a matrix-stack is always a LOAD_IDENTITY operation.

As an example consider if an application where to draw three rectangles
A, B and C something like this:

cogl_framebuffer_scale (fb, 2, 2, 2);
cogl_framebuffer_push_matrix(fb);

  cogl_framebuffer_translate (fb, 10, 0, 0);

  cogl_framebuffer_push_matrix(fb);

    cogl_framebuffer_rotate (fb, 45, 0, 0, 1);
    cogl_framebuffer_draw_rectangle (...); /* A */

  cogl_framebuffer_pop_matrix(fb);

  cogl_framebuffer_draw_rectangle (...); /* B */

cogl_framebuffer_pop_matrix(fb);

cogl_framebuffer_push_matrix(fb);
  cogl_framebuffer_set_modelview_matrix (fb, &mv);
  cogl_framebuffer_draw_rectangle (...); /* C */
cogl_framebuffer_pop_matrix(fb);

That would result in a graph of nodes like this:

LOAD_IDENTITY
      |
    SCALE
    /     \
SAVE       LOAD
  |           |
TRANSLATE    RECTANGLE(C)
  |     \
SAVE    RECTANGLE(B)
  |
ROTATE
  |
RECTANGLE(A)

Each push adds a SAVE operation which serves as a marker to rewind too
when a corresponding pop is issued and also each SAVE node may also
store a cached matrix representing the composition of all its ancestor
nodes. This means if we repeatedly need to resolve a real CoglMatrix
for a given node then we don't need to repeat the composition.

Some advantages of this design are:
- A single pointer to any node in the graph can now represent a
  complete, immutable transformation that can be logged for example
  into a journal. Previously we were storing a full CoglMatrix in
  each journal entry which is 16 floats for the matrix itself as well
  as space for flags and another 16 floats for possibly storing a
  cache of the inverse. This means that we significantly reduce
  the size of the journal when drawing lots of primitives and we also
  avoid copying over 128 bytes per entry.
- It becomes much cheaper to check for equality. In cases where some
  (unlikely) false negatives are allowed simply comparing the pointers
  of two matrix stack graph entries is enough. Previously we would use
  memcmp() to compare matrices.
- It becomes easier to do comparisons of transformations. By looking
  for the common ancestry between nodes we can determine the operations
  that differentiate the transforms and use those to gain a high level
  understanding of the differences. For example we use this in the
  journal to be able to efficiently determine when two rectangle
  transforms only differ by some translation so that we can perform
  software clipping.

Reviewed-by: Neil Roberts <neil@linux.intel.com>

(cherry picked from commit f75aee93f6b293ca7a7babbd8fcc326ee6bf7aef)
2012-08-06 14:27:40 +01:00

140 lines
4.3 KiB
C

/*
* Cogl
*
* An object oriented GL/GLES Abstraction/Utility Layer
*
* Copyright (C) 2008,2009,2010 Intel Corporation.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library. If not, see
* <http://www.gnu.org/licenses/>.
*
*
*
* Authors:
* Neil Roberts <neil@linux.intel.com>
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "cogl-context-private.h"
#include "cogl-pipeline-private.h"
#include "cogl-pipeline-state-private.h"
#include "cogl-pipeline-opengl-private.h"
#include "cogl-framebuffer-private.h"
#ifdef COGL_PIPELINE_VERTEND_FIXED
#include "cogl-internal.h"
#include "cogl-context-private.h"
#include "cogl-object-private.h"
#include "cogl-program-private.h"
const CoglPipelineVertend _cogl_pipeline_fixed_vertend;
static CoglBool
_cogl_pipeline_vertend_fixed_start (CoglPipeline *pipeline,
int n_layers,
unsigned long pipelines_difference,
int n_tex_coord_attribs)
{
CoglProgram *user_program;
_COGL_GET_CONTEXT (ctx, FALSE);
if (G_UNLIKELY (COGL_DEBUG_ENABLED (COGL_DEBUG_DISABLE_FIXED)))
return FALSE;
if (ctx->driver == COGL_DRIVER_GLES2)
return FALSE;
/* Vertex snippets are only supported in the GLSL fragend */
if (_cogl_pipeline_has_vertex_snippets (pipeline))
return FALSE;
/* If there is a user program with a vertex shader then the
appropriate backend for that language should handle it. We can
still use the fixed vertex backend if the program only contains
a fragment shader */
user_program = cogl_pipeline_get_user_program (pipeline);
if (user_program != COGL_INVALID_HANDLE &&
_cogl_program_has_vertex_shader (user_program))
return FALSE;
_cogl_use_vertex_program (0, COGL_PIPELINE_PROGRAM_TYPE_FIXED);
return TRUE;
}
static CoglBool
_cogl_pipeline_vertend_fixed_add_layer (CoglPipeline *pipeline,
CoglPipelineLayer *layer,
unsigned long layers_difference,
CoglFramebuffer *framebuffer)
{
CoglContext *ctx = framebuffer->context;
int unit_index = _cogl_pipeline_layer_get_unit_index (layer);
CoglTextureUnit *unit = _cogl_get_texture_unit (unit_index);
if (layers_difference & COGL_PIPELINE_LAYER_STATE_USER_MATRIX)
{
CoglPipelineLayerState state = COGL_PIPELINE_LAYER_STATE_USER_MATRIX;
CoglPipelineLayer *authority =
_cogl_pipeline_layer_get_authority (layer, state);
CoglMatrixEntry *matrix_entry;
_cogl_matrix_stack_set (unit->matrix_stack,
&authority->big_state->matrix);
_cogl_set_active_texture_unit (unit_index);
matrix_entry = unit->matrix_stack->last_entry;
_cogl_matrix_entry_flush_to_gl_builtins (ctx, matrix_entry,
COGL_MATRIX_TEXTURE,
framebuffer,
FALSE /* enable flip */);
}
return TRUE;
}
static CoglBool
_cogl_pipeline_vertend_fixed_end (CoglPipeline *pipeline,
unsigned long pipelines_difference)
{
_COGL_GET_CONTEXT (ctx, FALSE);
if (pipelines_difference & COGL_PIPELINE_STATE_POINT_SIZE)
{
CoglPipeline *authority =
_cogl_pipeline_get_authority (pipeline, COGL_PIPELINE_STATE_POINT_SIZE);
GE( ctx, glPointSize (authority->big_state->point_size) );
}
return TRUE;
}
const CoglPipelineVertend _cogl_pipeline_fixed_vertend =
{
_cogl_pipeline_vertend_fixed_start,
_cogl_pipeline_vertend_fixed_add_layer,
_cogl_pipeline_vertend_fixed_end,
NULL, /* pipeline_change_notify */
NULL /* layer_change_notify */
};
#endif /* COGL_PIPELINE_VERTEND_FIXED */