Function calcMaxDepthComplexity

OpenCSG/src/primitiveHelper.cpp:79–124

    namespace OpenGL {

        unsigned int calcMaxDepthComplexity(const std::vector<Primitive*>& primitives,
                                            const PCArea& area) {

            glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);

            glDisable(GL_DEPTH_TEST);
            glStencilMask(255);
            glEnable(GL_STENCIL_TEST);
            glStencilFunc(GL_ALWAYS, 0, 255);
            glStencilOp(GL_INCR, GL_INCR, GL_INCR);

            glEnable(GL_CULL_FACE);

            for (std::vector<Primitive*>::const_iterator itr = primitives.begin(); itr != primitives.end(); ++itr) {
                glCullFace((*itr)->getOperation() == Intersection ? GL_BACK : GL_FRONT);
                (*itr)->render();
            }

            glDisable(GL_CULL_FACE);
            glDisable(GL_STENCIL_TEST);
            glEnable(GL_DEPTH_TEST);

            int dx = area.maxx - area.minx;
            int dy = area.maxy - area.miny;

            std::size_t size = static_cast<std::size_t>(dx) * dy;
            GLubyte * buf = new GLubyte[size];

            glPixelStorei(GL_PACK_SWAP_BYTES, GL_FALSE);
            glPixelStorei(GL_PACK_ALIGNMENT, 1);
            glPixelStorei(GL_PACK_ROW_LENGTH, 0);
            glPixelStorei(GL_PACK_SKIP_ROWS, 0);
            glPixelStorei(GL_PACK_SKIP_PIXELS, 0);

            // This is pathologically slow on ATI HD4670 if not the complete viewport is read back.
            // So better always read the complete viewport or make this configurable?
            glReadPixels(area.minx, area.miny, dx, dy, GL_STENCIL_INDEX, GL_UNSIGNED_BYTE, buf);

            unsigned char m = *std::max_element(buf, buf+size);

            unsigned int max = m;

            delete[] buf;

            return max;
        }

        void renderLayer(unsigned int layer, const std::vector<Primitive*>& primitives) {
            glStencilFunc(GL_EQUAL, layer, 255);