/* Setup pointer to input attributes */
machine->Attribs = span->array->attribs;
- /* Store front/back facing value in register FOGC.Y */
- machine->Attribs[FRAG_ATTRIB_FOGC][col][1] = (GLfloat) ctx->_Facing;
+ machine->DerivX = (GLfloat (*)[4]) span->attrStepX;
+ machine->DerivY = (GLfloat (*)[4]) span->attrStepY;
+ machine->NumDeriv = FRAG_ATTRIB_MAX;
+
+ if (ctx->Shader.CurrentProgram) {
+ /* Store front/back facing value in register FOGC.Y */
+ machine->Attribs[FRAG_ATTRIB_FOGC][col][1] = (GLfloat) ctx->_Facing;
+ }
machine->CurElement = col;