This is a tutorial on how to fix the negative lighting bug which happens on some cards, after applying the colored lighting tutorial to your engine/source. Thanks to Ender it's fixed now. Open up gl_rsurf.c and replace the r_blendlightmaps with this function, new parts are in blue. /* ================ R_BlendLightmaps ================ */ void R_BlendLightmaps (void) { int i, j; glpoly_t *p; float *v; glRect_t *theRect; if (r_fullbright.value) return; if (!gl_texsort.value) return; glDepthMask (0); // don't bother writing Z // Ender - Fix negative lighting... with negative lighting. Wee :) if (gl_lightmap_format == GL_INTENSITY) { glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE); glColor4f (0,0,0,1); glBlendFunc (GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); } else { glBlendFunc (GL_ZERO, GL_ONE_MINUS_SRC_COLOR); } // Ender - End if (!r_lightmap.value) { glEnable (GL_BLEND); } for (i=0 ; i |