| 73 | }; |
| 74 | |
| 75 | void SCSChannelManagerAlphaOnly::merge() { |
| 76 | |
| 77 | ProjTextureSetup setup = FixedFunction; |
| 78 | setupProjectiveTexture(setup); |
| 79 | |
| 80 | glEnable(GL_ALPHA_TEST); |
| 81 | glEnable(GL_CULL_FACE); |
| 82 | glEnable(GL_DEPTH_TEST); |
| 83 | glDepthFunc(GL_LESS); |
| 84 | glDepthMask(GL_TRUE); |
| 85 | glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE); |
| 86 | |
| 87 | std::vector<Channel> channels = occupied(); |
| 88 | for (std::vector<Channel>::const_iterator c = channels.begin(); c!=channels.end(); ++c) { |
| 89 | |
| 90 | setupTexEnv(*c); |
| 91 | scissor->recall(*c); |
| 92 | scissor->enableScissor(); |
| 93 | |
| 94 | const std::vector<Primitive*> primitives = getPrimitives(*c); |
| 95 | for (std::vector<Primitive*>::const_iterator j = primitives.begin(); j != primitives.end(); ++j) { |
| 96 | glCullFace((*j)->getOperation() == Intersection ? GL_BACK : GL_FRONT); |
| 97 | RenderData* primitiveData = getRenderData(*j); |
| 98 | GLubyte id = primitiveData->bufferId.a; |
| 99 | |
| 100 | // Here is an interesting bug, which happened on an ATI HD4670, but actually |
| 101 | // might happen on every hardware. I am not sure whether it can be solved |
| 102 | // correctly. |
| 103 | |
| 104 | // Problem is that in optimized mode with some compilers (VC6, Visual Studio 2003 |
| 105 | // in particular), when setting the alpha func as follows: |
| 106 | // glAlphaFunc(GL_EQUAL, static_cast<float>(id) / 255.0f); |
| 107 | // the division is optimized as multiplication with 1.0f/255.0f. |
| 108 | // This is a fine and valid optimization. Unfortunately, the results |
| 109 | // are not exactly the same as the direct division for some ids. |
| 110 | // Which is apparently what the ATI driver is doing internally. |
| 111 | // So with comparison with GL_EQUAL fails. |
| 112 | |
| 113 | // Fortunately the OpenGL standard enforces that the mapping of color byte |
| 114 | // values to float fragment values be done by division. So if the |
| 115 | // solution found below (just working at double precision) proves |
| 116 | // to work once, it should work forever, such that a precompiling |
| 117 | // lookup table containing the correct alpha reference values is |
| 118 | // not required. However a bad feeling remains. |
| 119 | |
| 120 | // The SCSChannelManagerFragmentProgram path implemented below should fix this. |
| 121 | |
| 122 | double alpha = static_cast<double>(id) / 255.0; |
| 123 | GLfloat fAlpha = static_cast<float>(alpha); |
| 124 | glAlphaFunc(GL_EQUAL, fAlpha); |
| 125 | |
| 126 | (*j)->render(); |
| 127 | } |
| 128 | } |
| 129 | |
| 130 | scissor->disableScissor(); |
| 131 | |
| 132 | glDisable(GL_ALPHA_TEST); |
nothing calls this directly
no test coverage detected