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cogl-pipeline-glsl: Generate the alpha test snippet under GLES2

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GLES2 has no glAlphaFunc function so we need to simulate the behaviour
in the fragment shader. The alpha test function is simulated with an
if-statement and a discard statement. The reference value is stored as
a uniform.
This commit is contained in:
Neil Roberts 2010-11-22 18:33:49 +00:00
parent 0a314a752d
commit a86a1df372
1 changed files with 140 additions and 4 deletions
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144
cogl/cogl-pipeline-glsl.c
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@ -61,6 +61,7 @@
#define glDeleteShader ctx->drv.pf_glDeleteShader
#define glGetUniformLocation ctx->drv.pf_glGetUniformLocation
#define glUniform1i ctx->drv.pf_glUniform1i
#define glUniform1f ctx->drv.pf_glUniform1f
#define glUniform4fv ctx->drv.pf_glUniform4fv
#endif /* HAVE_COGL_GLES2 */
@ -117,6 +118,12 @@ typedef struct _GlslProgramState
custom uniforms. This is a massive hack but it can go away once
this GLSL backend starts generating its own shaders */
GLuint gles2_program;
/* Under GLES2 the alpha test is implemented in the shader. We need
a uniform for the reference value */
gboolean alpha_test_reference_used;
gboolean dirty_alpha_test_reference;
GLint alpha_test_reference_uniform;
#endif
/* We need to track the last pipeline that the program was used with
@ -416,6 +423,12 @@ _cogl_pipeline_backend_glsl_start (CoglPipeline *pipeline,
"main ()\n"
"{\n");
#ifdef HAVE_COGL_GLES2
priv->glsl_program_state->alpha_test_reference_uniform = -1;
priv->glsl_program_state->alpha_test_reference_used = FALSE;
priv->glsl_program_state->dirty_alpha_test_reference = FALSE;
#endif
for (i = 0; i < n_layers; i++)
{
priv->glsl_program_state->unit_state[i].sampled = FALSE;
@ -878,6 +891,103 @@ update_constants_cb (CoglPipeline *pipeline,
return TRUE;
}
/* GLES2 doesn't have alpha testing so we need to implement it in the
shader */
#ifdef HAVE_COGL_GLES2
static void
add_alpha_test_snippet (CoglPipeline *pipeline,
GlslProgramState *glsl_program_state)
{
CoglPipelineAlphaFunc alpha_func;
alpha_func = cogl_pipeline_get_alpha_test_function (pipeline);
if (alpha_func == COGL_PIPELINE_ALPHA_FUNC_ALWAYS)
/* Do nothing */
return;
if (alpha_func == COGL_PIPELINE_ALPHA_FUNC_NEVER)
{
/* Always discard the fragment */
g_string_append (glsl_program_state->source,
" discard;\n");
return;
}
/* For all of the other alpha functions we need a uniform for the
reference */
glsl_program_state->alpha_test_reference_used = TRUE;
glsl_program_state->dirty_alpha_test_reference = TRUE;
g_string_append (glsl_program_state->header,
"uniform float _cogl_alpha_test_ref;\n");
g_string_append (glsl_program_state->source,
" if (cogl_color_out.a ");
switch (alpha_func)
{
case COGL_PIPELINE_ALPHA_FUNC_LESS:
g_string_append (glsl_program_state->source, ">=");
break;
case COGL_PIPELINE_ALPHA_FUNC_EQUAL:
g_string_append (glsl_program_state->source, "!=");
break;
case COGL_PIPELINE_ALPHA_FUNC_LEQUAL:
g_string_append (glsl_program_state->source, ">");
break;
case COGL_PIPELINE_ALPHA_FUNC_GREATER:
g_string_append (glsl_program_state->source, "<=");
break;
case COGL_PIPELINE_ALPHA_FUNC_NOTEQUAL:
g_string_append (glsl_program_state->source, "==");
break;
case COGL_PIPELINE_ALPHA_FUNC_GEQUAL:
g_string_append (glsl_program_state->source, "< ");
break;
case COGL_PIPELINE_ALPHA_FUNC_ALWAYS:
case COGL_PIPELINE_ALPHA_FUNC_NEVER:
g_assert_not_reached ();
break;
}
g_string_append (glsl_program_state->source,
" _cogl_alpha_test_ref)\n discard;\n");
}
static void
update_alpha_test_reference (CoglPipeline *pipeline,
GLuint gl_program,
GlslProgramState *glsl_program_state)
{
float alpha_reference;
if (glsl_program_state->dirty_alpha_test_reference)
{
if (glsl_program_state->alpha_test_reference_uniform == -1)
{
GE_RET( glsl_program_state->alpha_test_reference_uniform,
glGetUniformLocation (gl_program,
"_cogl_alpha_test_ref") );
g_return_if_fail (glsl_program_state->
alpha_test_reference_uniform != -1);
}
alpha_reference = cogl_pipeline_get_alpha_test_reference (pipeline);
GE( glUniform1f (glsl_program_state->alpha_test_reference_uniform,
alpha_reference) );
glsl_program_state->dirty_alpha_test_reference = FALSE;
}
}
#endif /* HAVE_COGL_GLES2 */
gboolean
_cogl_pipeline_backend_glsl_end (CoglPipeline *pipeline,
unsigned long pipelines_difference)
@ -934,6 +1044,10 @@ _cogl_pipeline_backend_glsl_end (CoglPipeline *pipeline,
0 /* no application private data */);
COGL_COUNTER_INC (_cogl_uprof_context, backend_glsl_compile_counter);
#ifdef HAVE_COGL_GLES2
add_alpha_test_snippet (pipeline, glsl_program_state);
#endif
g_string_append (glsl_program_state->source, "}\n");
if (G_UNLIKELY (cogl_debug_flags & COGL_DEBUG_SHOW_SOURCE))
@ -1016,6 +1130,19 @@ _cogl_pipeline_backend_glsl_end (CoglPipeline *pipeline,
update_constants_cb,
&state);
#ifdef HAVE_COGL_GLES2
if (glsl_program_state->alpha_test_reference_used)
{
if (gl_program_changed)
glsl_program_state->alpha_test_reference_uniform = -1;
if (gl_program_changed ||
glsl_program_state->last_used_for_pipeline != pipeline)
glsl_program_state->dirty_alpha_test_reference = TRUE;
update_alpha_test_reference (pipeline, gl_program, glsl_program_state);
}
#endif
if (user_program)
_cogl_program_flush_uniforms (user_program,
gl_program,
@ -1035,13 +1162,22 @@ _cogl_pipeline_backend_glsl_pre_change_notify (CoglPipeline *pipeline,
{
static const unsigned long fragment_op_changes =
COGL_PIPELINE_STATE_LAYERS |
#ifdef COGL_HAS_GLES2
COGL_PIPELINE_STATE_ALPHA_FUNC |
#endif
COGL_PIPELINE_STATE_USER_SHADER;
/* TODO: COGL_PIPELINE_STATE_FOG */
if (!(change & fragment_op_changes))
return;
dirty_glsl_program_state (pipeline);
if ((change & fragment_op_changes))
dirty_glsl_program_state (pipeline);
#ifdef COGL_HAS_GLES2
else if ((change & COGL_PIPELINE_STATE_ALPHA_FUNC_REFERENCE))
{
GlslProgramState *glsl_program_state =
get_glsl_program_state (pipeline);
glsl_program_state->dirty_alpha_test_reference = TRUE;
}
#endif
}
/* NB: layers are considered immutable once they have any dependants