static void compute_fog_blend_factors	(	GLcontext *	ctx,
		GLvector4f *	out,
		const GLvector4f *	in
	)		`[static]`

Compute per-vertex fog blend factors from fog coordinates by evaluating the GL_LINEAR, GL_EXP or GL_EXP2 fog function. Fog coordinates are distances from the eye (typically between the near and far clip plane distances). Note that fogcoords may be negative, if eye z is source absolute value must be taken earlier. Fog blend factors are in the range [0,1].

Definition at line 98 of file t_vb_fog.c.

Referenced by run_fog_stage().

{
   GLfloat end  = ctx->Fog.End;
   GLfloat *v = in->start;
   GLuint stride = in->stride;
   GLuint n = in->count;
   GLfloat (*data)[4] = out->data;
   GLfloat d;
   GLuint i;

   out->count = in->count;

   switch (ctx->Fog.Mode) {
   case GL_LINEAR:
      if (ctx->Fog.Start == ctx->Fog.End)
         d = 1.0F;
      else
         d = 1.0F / (ctx->Fog.End - ctx->Fog.Start);
      for ( i = 0 ; i < n ; i++, STRIDE_F(v, stride)) {
         const GLfloat z = *v;
         GLfloat f = (end - z) * d;
     data[i][0] = CLAMP(f, 0.0F, 1.0F);
      }
      break;
   case GL_EXP:
      d = ctx->Fog.Density;
      for ( i = 0 ; i < n ; i++, STRIDE_F(v,stride)) {
         const GLfloat z = *v;
         NEG_EXP( data[i][0], d * z );
      }
      break;
   case GL_EXP2:
      d = ctx->Fog.Density*ctx->Fog.Density;
      for ( i = 0 ; i < n ; i++, STRIDE_F(v, stride)) {
         const GLfloat z = *v;
         NEG_EXP( data[i][0], d * z * z );
      }
      break;
   default:
      _mesa_problem(ctx, "Bad fog mode in make_fog_coord");
      return;
   }
}

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