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mutter-performance-source/cogl/cogl-matrix-stack.h
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

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/*
* Cogl
*
* An object oriented GL/GLES Abstraction/Utility Layer
*
* Copyright (C) 2009,2010,2012 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:
* Havoc Pennington <hp@pobox.com> for litl
* Robert Bragg <robert@linux.intel.com>
*/
#ifndef __COGL_MATRIX_STACK_H
#define __COGL_MATRIX_STACK_H
#include "cogl-object-private.h"
#include "cogl-matrix.h"
#include "cogl-context.h"
#include "cogl-framebuffer.h"
typedef enum _CoglMatrixOp
{
COGL_MATRIX_OP_LOAD_IDENTITY,
COGL_MATRIX_OP_TRANSLATE,
COGL_MATRIX_OP_ROTATE,
COGL_MATRIX_OP_SCALE,
COGL_MATRIX_OP_MULTIPLY,
COGL_MATRIX_OP_LOAD,
COGL_MATRIX_OP_SAVE,
} CoglMatrixOp;
typedef struct _CoglMatrixEntry CoglMatrixEntry;
struct _CoglMatrixEntry
{
CoglMatrixOp op;
CoglMatrixEntry *parent;
unsigned int ref_count;
/* used for performance tracing */
int composite_gets;
};
typedef struct _CoglMatrixEntryTranslate
{
CoglMatrixEntry _parent_data;
float x;
float y;
float z;
} CoglMatrixEntryTranslate;
typedef struct _CoglMatrixEntryRotate
{
CoglMatrixEntry _parent_data;
float angle;
float x;
float y;
float z;
} CoglMatrixEntryRotate;
typedef struct _CoglMatrixEntryScale
{
CoglMatrixEntry _parent_data;
float x;
float y;
float z;
} CoglMatrixEntryScale;
typedef struct _CoglMatrixEntryMultiply
{
CoglMatrixEntry _parent_data;
CoglMatrix *matrix;
} CoglMatrixEntryMultiply;
typedef struct _CoglMatrixEntryLoad
{
CoglMatrixEntry _parent_data;
CoglMatrix *matrix;
} CoglMatrixEntryLoad;
typedef struct _CoglMatrixEntrySave
{
CoglMatrixEntry _parent_data;
CoglBool cache_valid;
CoglMatrix *cache;
} CoglMatrixEntrySave;
typedef union _CoglMatrixEntryFull
{
CoglMatrixEntry any;
CoglMatrixEntryTranslate translate;
CoglMatrixEntryRotate rotae;
CoglMatrixEntryScale scale;
CoglMatrixEntryMultiply multiply;
CoglMatrixEntryLoad load;
CoglMatrixEntrySave save;
} CoglMatrixEntryFull;
typedef struct _CoglMatrixStack
{
CoglObject _parent;
CoglMatrixEntry *last_entry;
} CoglMatrixStack;
typedef struct _CoglMatrixEntryCache
{
CoglMatrixEntry *entry;
CoglBool flushed_identity;
CoglBool flipped;
} CoglMatrixEntryCache;
CoglMatrixStack *
_cogl_matrix_stack_new (void);
void
_cogl_matrix_stack_push (CoglMatrixStack *stack);
void
_cogl_matrix_stack_pop (CoglMatrixStack *stack);
void
_cogl_matrix_entry_identity_init (CoglMatrixEntry *entry);
void
_cogl_matrix_stack_load_identity (CoglMatrixStack *stack);
void
_cogl_matrix_stack_scale (CoglMatrixStack *stack,
float x,
float y,
float z);
void
_cogl_matrix_stack_translate (CoglMatrixStack *stack,
float x,
float y,
float z);
void
_cogl_matrix_stack_rotate (CoglMatrixStack *stack,
float angle,
float x,
float y,
float z);
void
_cogl_matrix_stack_multiply (CoglMatrixStack *stack,
const CoglMatrix *matrix);
void
_cogl_matrix_stack_frustum (CoglMatrixStack *stack,
float left,
float right,
float bottom,
float top,
float z_near,
float z_far);
void
_cogl_matrix_stack_perspective (CoglMatrixStack *stack,
float fov_y,
float aspect,
float z_near,
float z_far);
void
_cogl_matrix_stack_orthographic (CoglMatrixStack *stack,
float x_1,
float y_1,
float x_2,
float y_2,
float near,
float far);
CoglBool
_cogl_matrix_stack_get_inverse (CoglMatrixStack *stack,
CoglMatrix *inverse);
/* NB: This function only *sometimes* returns a pointer to a matrix if
* the matrix returned didn't need to be composed of multiple
* operations */
CoglMatrix *
_cogl_matrix_stack_get (CoglMatrixStack *stack,
CoglMatrix *matrix);
/* NB: This function only *sometimes* returns a pointer to a matrix if
* the matrix returned didn't need to be composed of multiple
* operations */
CoglMatrix *
_cogl_matrix_entry_get (CoglMatrixEntry *entry,
CoglMatrix *matrix);
void
_cogl_matrix_stack_set (CoglMatrixStack *stack,
const CoglMatrix *matrix);
CoglBool
_cogl_matrix_entry_calculate_translation (CoglMatrixEntry *entry0,
CoglMatrixEntry *entry1,
float *x,
float *y,
float *z);
/* If this returns TRUE then the entry is definitely the identity
* matrix. If it returns FALSE it may or may not be the identity
* matrix but no expensive comparison is performed to verify it. */
CoglBool
_cogl_matrix_entry_has_identity_flag (CoglMatrixEntry *entry);
CoglBool
_cogl_matrix_entry_fast_equal (CoglMatrixEntry *entry0,
CoglMatrixEntry *entry1);
CoglBool
_cogl_matrix_entry_equal (CoglMatrixEntry *entry0,
CoglMatrixEntry *entry1);
void
_cogl_matrix_entry_print (CoglMatrixEntry *entry);
CoglMatrixEntry *
_cogl_matrix_entry_ref (CoglMatrixEntry *entry);
void
_cogl_matrix_entry_unref (CoglMatrixEntry *entry);
typedef enum {
COGL_MATRIX_MODELVIEW,
COGL_MATRIX_PROJECTION,
COGL_MATRIX_TEXTURE
} CoglMatrixMode;
void
_cogl_matrix_entry_flush_to_gl_builtins (CoglContext *ctx,
CoglMatrixEntry *entry,
CoglMatrixMode mode,
CoglFramebuffer *framebuffer,
CoglBool disable_flip);
void
_cogl_matrix_entry_cache_init (CoglMatrixEntryCache *cache);
CoglBool
_cogl_matrix_entry_cache_maybe_update (CoglMatrixEntryCache *cache,
CoglMatrixEntry *entry,
CoglBool flip);
void
_cogl_matrix_entry_cache_destroy (CoglMatrixEntryCache *cache);
CoglBool
_cogl_is_matrix_stack (void *object);
#endif /* __COGL_MATRIX_STACK_H */
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