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The "alpha" blend mode now outputs more useful/intuitive alpha values (thanks Boolsheet)

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See https://love2d.org/forums/viewtopic.php?f=4&t=16223 and http://www.opengl.org/discussion_boards/showthread.php/167554-FBO-and-blending
This commit is contained in:
Alex Szpakowski
2013-02-26 21:44:01 -04:00
parent 0be26b7678
commit 395a1dbced
2 changed files with 122 additions and 50 deletions
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src/modules/graphics/opengl/Graphics.cpp
+97 -37
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@@ -114,7 +114,7 @@ bool Graphics::setMode(int width, int height, bool fullscreen, bool vsync, int f
// Unload all volatile objects. These must be reloaded after
// the display mode change.
Volatile::unloadAll();
uninitializeContext();
bool success = currentWindow->setWindow(width, height, fullscreen, vsync, fsaa);
@@ -502,37 +502,76 @@ Font *Graphics::getFont() const
void Graphics::setBlendMode(Graphics::BlendMode mode)
{
if (GLEE_VERSION_1_4 || GLEE_ARB_imaging)
const int gl_1_4 = GLEE_VERSION_1_4;
GLenum func = GL_FUNC_ADD;
GLenum src_rgb = GL_ONE;
GLenum src_a = GL_ONE;
GLenum dst_rgb = GL_ZERO;
GLenum dst_a = GL_ZERO;
switch (mode)
{
if (mode == BLEND_SUBTRACTIVE)
glBlendEquation(GL_FUNC_REVERSE_SUBTRACT);
case BLEND_ALPHA:
if (gl_1_4 || GLEE_EXT_blend_func_separate)
{
src_rgb = GL_SRC_ALPHA;
src_a = GL_ONE;
dst_rgb = dst_a = GL_ONE_MINUS_SRC_ALPHA;
}
else
glBlendEquation(GL_FUNC_ADD);
{
// Fallback for OpenGL implementations without support for separate blend functions.
// This will most likely only be used for the Microsoft software renderer and
// since it's still stuck with OpenGL 1.1, the only expected difference is a
// different alpha value when reading back the default framebuffer (newScreenshot).
src_rgb = src_a = GL_SRC_ALPHA;
dst_rgb = dst_a = GL_ONE_MINUS_SRC_ALPHA;
}
break;
case BLEND_MULTIPLICATIVE:
src_rgb = src_a = GL_DST_COLOR;
dst_rgb = dst_a = GL_ZERO;
break;
case BLEND_PREMULTIPLIED:
src_rgb = src_a = GL_ONE;
dst_rgb = dst_a = GL_ONE_MINUS_SRC_ALPHA;
break;
case BLEND_SUBTRACTIVE:
func = GL_FUNC_REVERSE_SUBTRACT;
case BLEND_ADDITIVE:
src_rgb = src_a = GL_SRC_ALPHA;
dst_rgb = dst_a = GL_ONE;
break;
case BLEND_NONE:
default:
src_rgb = src_a = GL_ONE;
dst_rgb = dst_a = GL_ZERO;
break;
}
if (gl_1_4 || GLEE_ARB_imaging)
glBlendEquation(func);
else if (GLEE_EXT_blend_minmax && GLEE_EXT_blend_subtract)
{
if (mode == BLEND_SUBTRACTIVE)
glBlendEquationEXT(GL_FUNC_REVERSE_SUBTRACT_EXT);
else
glBlendEquationEXT(GL_FUNC_ADD_EXT);
}
glBlendEquationEXT(func);
else
{
if (mode == BLEND_SUBTRACTIVE)
throw Exception("This graphics card does not support the subtract blend mode!");
if (func == GL_FUNC_REVERSE_SUBTRACT)
throw Exception("This graphics card does not support the subtractive blend mode!");
// GL_FUNC_ADD is the default even without access to glBlendEquation, so that'll still work.
}
if (mode == BLEND_ALPHA)
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
else if (mode == BLEND_MULTIPLICATIVE)
glBlendFunc(GL_DST_COLOR, GL_ZERO);
else if (mode == BLEND_PREMULTIPLIED)
glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
else if (mode == BLEND_NONE)
glBlendFunc(GL_ONE, GL_ZERO);
else // mode == BLEND_ADDITIVE || mode == BLEND_SUBTRACTIVE
glBlendFunc(GL_SRC_ALPHA, GL_ONE);
if (src_rgb == src_a && dst_rgb == dst_a)
glBlendFunc(src_rgb, dst_rgb);
else
{
if (gl_1_4)
glBlendFuncSeparate(src_rgb, dst_rgb, src_a, dst_a);
else if (GLEE_EXT_blend_func_separate)
glBlendFuncSeparateEXT(src_rgb, dst_rgb, src_a, dst_a);
else
throw Exception("This graphics card does not support separated rgb and alpha blend functions!");
}
}
void Graphics::setColorMode(Graphics::ColorMode mode)
@@ -551,29 +590,50 @@ void Graphics::setColorMode(Graphics::ColorMode mode)
Graphics::BlendMode Graphics::getBlendMode() const
{
GLint dst, src;
glGetIntegerv(GL_BLEND_DST, &dst);
glGetIntegerv(GL_BLEND_SRC, &src);
const int gl_1_4 = GLEE_VERSION_1_4;
GLint src_rgb, src_a, dst_rgb, dst_a;
GLint equation = GL_FUNC_ADD;
if (GLEE_VERSION_1_4 || GLEE_ARB_imaging || (GLEE_EXT_blend_minmax && GLEE_EXT_blend_subtract))
if (gl_1_4 || GLEE_EXT_blend_func_separate)
{
glGetIntegerv(GL_BLEND_SRC_RGB, &src_rgb);
glGetIntegerv(GL_BLEND_SRC_ALPHA, &src_a);
glGetIntegerv(GL_BLEND_DST_RGB, &dst_rgb);
glGetIntegerv(GL_BLEND_DST_ALPHA, &dst_a);
}
else
{
glGetIntegerv(GL_BLEND_SRC, &src_rgb);
glGetIntegerv(GL_BLEND_DST, &dst_rgb);
src_a = src_rgb;
dst_a = dst_rgb;
}
if (gl_1_4 || GLEE_ARB_imaging || (GLEE_EXT_blend_minmax && GLEE_EXT_blend_subtract))
glGetIntegerv(GL_BLEND_EQUATION, &equation);
if (equation == GL_FUNC_REVERSE_SUBTRACT) // && src == GL_SRC_ALPHA && dst == GL_ONE
return BLEND_SUBTRACTIVE;
else if (src == GL_SRC_ALPHA && dst == GL_ONE) // && equation == GL_FUNC_ADD
return BLEND_ADDITIVE;
else if (src == GL_SRC_ALPHA && dst == GL_ONE_MINUS_SRC_ALPHA) // && equation == GL_FUNC_ADD
// Everything else has equation == GL_FUNC_ADD.
else if (src_rgb == src_a && dst_rgb == dst_a)
{
if (src_rgb == GL_SRC_ALPHA && dst_rgb == GL_ONE)
return BLEND_ADDITIVE;
else if (src_rgb == GL_SRC_ALPHA && dst_rgb == GL_ONE_MINUS_SRC_ALPHA)
return BLEND_ALPHA; // alpha blend mode fallback for very old OpenGL versions.
else if (src_rgb == GL_DST_COLOR && dst_rgb == GL_ZERO)
return BLEND_MULTIPLICATIVE;
else if (src_rgb == GL_ONE && dst_rgb == GL_ONE_MINUS_SRC_ALPHA)
return BLEND_PREMULTIPLIED;
else if (src_rgb == GL_ONE && dst_rgb == GL_ZERO)
return BLEND_NONE;
}
else if (src_rgb == GL_SRC_ALPHA && src_a == GL_ONE &&
dst_rgb == GL_ONE_MINUS_SRC_ALPHA && dst_a == GL_ONE_MINUS_SRC_ALPHA)
return BLEND_ALPHA;
else if (src == GL_DST_COLOR && dst == GL_ZERO) // && equation == GL_FUNC_ADD
return BLEND_MULTIPLICATIVE;
else if (src == GL_ONE && dst == GL_ONE_MINUS_SRC_ALPHA) // && equation == GL_FUNC_ADD
return BLEND_PREMULTIPLIED;
else if (src == GL_ONE && dst == GL_ZERO)
return BLEND_NONE;
return BLEND_MAX_ENUM; // Should never be reached.
throw Exception("Unknown blend mode");
}
Graphics::ColorMode Graphics::getColorMode() const