Hi Ian, mesa-dev, I've been trying to implement ARB_viewport_array support on nv50, with little success. Christoph pointed out that if I write the gl_ViewportIndex value before each emit (rather than once at the top, as the piglit tests do it), everything magically starts working.
I glanced at http://www.opengl.org/sdk/docs/manglsl/xhtml/gl_ViewportIndex.xml which is a bit inconclusive: "The viewport index used will come from one of the vertices in the primitive being shaded. However, which vertex the viewport index comes from is implementation-defined, and so it is recommended to use the same viewport index for all vertices of a primitive." And there's various text about how if it's unset, it's undefined. But it's unclear what "set" means -- does it become unset after an EmitVertex() call or not? Actually Christoph just pointed out that EmitVertex says: "Emit the current values of output variables to the current output primitive. On return from this call, the values of output variables are undefined." So I guess the piglit tests should change? Could someone with actual understanding of GLSL/etc take a look and let me know whether I need to register gl_ViewportIndex (and, in all probability, gl_Layer) writes and then write the registered value on every EmitVertex in the driver, or whether the piglit tests should be changed? (An observation is that I did _not_ need to move the 'color' out into the loop in render-scissor, just gl_ViewportIndex -- but that could be an abberation of the nvidia geometry program execution logic.) Thanks, -ilia _______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/mesa-dev
