A few more tweaks to fog code.

Remove unneeded FABSF() macros.
Added blend factor clamping in a few spots.

src/mesa/swrast/s_fog.c

@@ -55,10 +55,12 @@ _swrast_z_to_fogfactor(GLcontext *ctx, GLfloat z)
    case GL_EXP:
       d = ctx->Fog.Density;
       f = (GLfloat) exp(-d * z);
+      f = CLAMP(f, 0.0F, 1.0F);
       return f;
    case GL_EXP2:
       d = ctx->Fog.Density;
       f = (GLfloat) exp(-(d * d * z * z));
+      f = CLAMP(f, 0.0F, 1.0F);
       return f;
    default:
       _mesa_problem(ctx, "Bad fog mode in _swrast_z_to_fogfactor");
@@ -110,7 +112,7 @@ _swrast_fog_rgba_span( const GLcontext *ctx, struct sw_span *span )
             GLuint i;
             for (i = 0; i < span->end; i++) {
                GLfloat f, oneMinusF;
-               f = (fogEnd - FABSF(fogCoord/w)) * fogScale;
+               f = (fogEnd - fogCoord / w) * fogScale;
                f = CLAMP(f, 0.0F, 1.0F);
                oneMinusF = 1.0F - f;
                rgba[i][RCOMP] = (GLchan) (f * rgba[i][RCOMP] + oneMinusF * rFog);
@@ -131,7 +133,8 @@ _swrast_fog_rgba_span( const GLcontext *ctx, struct sw_span *span )
             GLuint i;
             for (i = 0; i < span->end; i++) {
                GLfloat f, oneMinusF;
-               f = (GLfloat) exp(density * FABSF(fogCoord/w));
+               f = (GLfloat) exp(density * fogCoord / w);
+               f = CLAMP(f, 0.0F, 1.0F);
                oneMinusF = 1.0F - f;
                rgba[i][RCOMP] = (GLchan) (f * rgba[i][RCOMP] + oneMinusF * rFog);
                rgba[i][GCOMP] = (GLchan) (f * rgba[i][GCOMP] + oneMinusF * gFog);
@@ -242,7 +245,7 @@ _swrast_fog_ci_span( const GLcontext *ctx, struct sw_span *span )
             GLfloat w = haveW ? span->w : 1.0F;
             GLuint i;
             for (i = 0; i < span->end; i++) {
-               GLfloat f = (fogEnd - FABSF(fogCoord/w)) * fogScale;
+               GLfloat f = (fogEnd - fogCoord / w) * fogScale;
                f = CLAMP(f, 0.0F, 1.0F);
                index[i] = (GLuint) ((GLfloat) index[i] + (1.0F - f) * fogIndex);
                fogCoord += fogStep;
@@ -259,7 +262,8 @@ _swrast_fog_ci_span( const GLcontext *ctx, struct sw_span *span )
             GLfloat w = haveW ? span->w : 1.0F;
             GLuint i;
             for (i = 0; i < span->end; i++) {
-               GLfloat f = (GLfloat) exp(density * FABSF(fogCoord/w));
+               GLfloat f = (GLfloat) exp(density * fogCoord / w);
+               f = CLAMP(f, 0.0F, 1.0F);
                index[i] = (GLuint) ((GLfloat) index[i] + (1.0F - f) * fogIndex);
                fogCoord += fogStep;
                w += wStep;

src/mesa/tnl/t_vb_fog.c

@@ -113,7 +113,7 @@ compute_fog_blend_factors(GLcontext *ctx, GLvector4f *out, const GLvector4f *in)
       else
          d = 1.0F / (ctx->Fog.End - ctx->Fog.Start);
       for ( i = 0 ; i < n ; i++, STRIDE_F(v, stride)) {
-         const GLfloat z = FABSF(*v);
+         const GLfloat z = *v;
          GLfloat f = (end - z) * d;
 	 data[i][0] = CLAMP(f, 0.0F, 1.0F);
       }
@@ -121,7 +121,7 @@ compute_fog_blend_factors(GLcontext *ctx, GLvector4f *out, const GLvector4f *in)
    case GL_EXP:
       d = ctx->Fog.Density;
       for ( i = 0 ; i < n ; i++, STRIDE_F(v,stride)) {
-         const GLfloat z = FABSF(*v);
+         const GLfloat z = *v;
          NEG_EXP( data[i][0], d * z );
       }
       break;
@@ -165,10 +165,11 @@ run_fog_stage(GLcontext *ctx, struct tnl_pipeline_stage *stage)
 	  */
 	 input = &store->fogcoord;
 
-	 plane[0] = m[2];
-	 plane[1] = m[6];
-	 plane[2] = m[10];
-	 plane[3] = m[14];
+         /* NOTE: negate plane here so we get positive fog coords! */
+	 plane[0] = -m[2];
+	 plane[1] = -m[6];
+	 plane[2] = -m[10];
+	 plane[3] = -m[14];
 
 	 /* Full eye coords weren't required, just calculate the
 	  * eye Z values.