-
-/*
- * Apply fog to an array of RGBA pixels.
- * Input: n - number of pixels
- * z - array of integer depth values
- * red, green, blue, alpha - pixel colors
- * Output: red, green, blue, alpha - fogged pixel colors
- */
-void
-_mesa_fog_rgba_pixels( const GLcontext *ctx,
- GLuint n, const GLdepth z[], GLubyte rgba[][4] )
-{
- GLfloat c = ctx->ProjectionMatrix.m[10];
- GLfloat d = ctx->ProjectionMatrix.m[14];
- GLuint i;
-
- GLfloat rFog = ctx->Fog.Color[0] * 255.0F;
- GLfloat gFog = ctx->Fog.Color[1] * 255.0F;
- GLfloat bFog = ctx->Fog.Color[2] * 255.0F;
-
- GLfloat tz = ctx->Viewport.WindowMap.m[MAT_TZ];
- GLfloat szInv = 1.0F / ctx->Viewport.WindowMap.m[MAT_SZ];
-
- switch (ctx->Fog.Mode) {
- case GL_LINEAR:
- {
- GLfloat fogEnd = ctx->Fog.End;
- GLfloat fogScale = 1.0F / (ctx->Fog.End - ctx->Fog.Start);
- for (i=0;i<n;i++) {
- GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
- GLfloat eyez = -d / (c+ndcz);
- GLfloat f, g;
- if (eyez < 0.0) eyez = -eyez;
- f = (fogEnd - eyez) * fogScale;
- f = CLAMP( f, 0.0F, 1.0F );
- g = 1.0F - f;
- rgba[i][RCOMP] = (GLint) (f * rgba[i][RCOMP] + g * rFog);
- rgba[i][GCOMP] = (GLint) (f * rgba[i][GCOMP] + g * gFog);
- rgba[i][BCOMP] = (GLint) (f * rgba[i][BCOMP] + g * bFog);
- }
- }
- break;
- case GL_EXP:
- for (i=0;i<n;i++) {
- GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
- GLfloat eyez = d / (c+ndcz);
- GLfloat f, g;
- if (eyez < 0.0)
- eyez = -eyez;
- f = exp( -ctx->Fog.Density * eyez );
- g = 1.0F - f;
- rgba[i][RCOMP] = (GLint) (f * rgba[i][RCOMP] + g * rFog);
- rgba[i][GCOMP] = (GLint) (f * rgba[i][GCOMP] + g * gFog);
- rgba[i][BCOMP] = (GLint) (f * rgba[i][BCOMP] + g * bFog);
- }
- break;
- case GL_EXP2:
- {
- GLfloat negDensitySquared = -ctx->Fog.Density * ctx->Fog.Density;
- for (i=0;i<n;i++) {
- GLfloat ndcz = ((GLfloat) z[i] - tz) * szInv;
- GLfloat eyez = d / (c+ndcz);
- GLfloat f, g;
- GLfloat tmp = negDensitySquared * eyez * eyez;
-#ifdef __alpha__
- /* XXX this underflow check may be needed for other systems */
- if (tmp < FLT_MIN_10_EXP)
- f = exp( FLT_MIN_10_EXP );
- else
-#endif
- f = exp( tmp );
- g = 1.0F - f;
- rgba[i][RCOMP] = (GLint) (f * rgba[i][RCOMP] + g * rFog);
- rgba[i][GCOMP] = (GLint) (f * rgba[i][GCOMP] + g * gFog);
- rgba[i][BCOMP] = (GLint) (f * rgba[i][BCOMP] + g * bFog);
- }
- }
- break;
- default:
- gl_problem(ctx, "Bad fog mode in _mesa_fog_rgba_pixels");
- return;
- }