Here's a quick little list of things that'll need to be addressed in the DRI drivers if we want to update them to run shading language programs.
The drivers that currently support GL_ARB_vertex/fragment_program are the likely candidates. 1. New instructions The shading language has conditionals, loops, return statements, etc. These can be expressed using the new high-level IF/ELSE/ENDIF, BGNLOOP/ENDLOOP, BRK, CONT, etc. opcodes, or simple jumps/branches (see prog_instruction.h). The compiler can emit either kind of code. In any case, support for the new instructions would have to be added in the driver code which translates Mesa GPU instructions into hardware instructions. It's not uncommon for shaders to have no branches or loops, resulting in simple, straight-line code. So some shaders could be run on hardware that might not support shaders in general. You'd have to scan the program to see what kind of instructions are used. But we might ask ourselves if we really want to expose the shading language in drivers that can't actually run shaders with conditionals, etc. 2. Varying variables Varying variables are general-purpose values that are transmitted from the vertex shader to the fragment shader. They're like extra sets of texture coords that get interpolated during rasterization. So, drivers will need some work to support those. 3. Extra validation There's new shader-related state that needs to be handled. One example is uniform variables. Uniforms are shader variables that are constant over glBegin/glEnd. They're stored in Mesa's gl_program_parameter_list lists just like other constants so it shouldn't be too hard to implement them, but it's a new PROGRAM_UNIFORM parameter type. We may also need to add some new ctx->Driver.foo() hooks for some shading language things. I haven't investigated that enough to say for sure though. I'll try to answer questions about these things if anyone decides to tackle this project. -Brian ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Mesa3d-dev mailing list Mesa3d-dev@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mesa3d-dev
