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Diffstat (limited to 'src/mesa/tnl_dd/imm/NOTES.imm')
| -rw-r--r-- | src/mesa/tnl_dd/imm/NOTES.imm | 112 |
1 files changed, 112 insertions, 0 deletions
diff --git a/src/mesa/tnl_dd/imm/NOTES.imm b/src/mesa/tnl_dd/imm/NOTES.imm new file mode 100644 index 0000000000..9b2bd65e4b --- /dev/null +++ b/src/mesa/tnl_dd/imm/NOTES.imm @@ -0,0 +1,112 @@ + +NOTE: + +These files are incomplete. They do not yet form a working +implementation of hte concepts discused below. + + +OVERVIEW + +The t_dd_imm_* files form a set of templates to produce driver - +specific software tnl modules for a small subset of transformation and +lighting states. + +The approach is quite different to the large vertex buffers of the +src/tnl module, and is based around a cache of four recent vertices +and a 'current' vertex which is updated directly from the Color, +Normal, Texcoord, SecondaryColor and Fog entrypoints. + +The current vertex is actually a composite of the ctx->Current values +and a partial hardware vertex maintained where the hardware values +differ from those in ctx->Current. For example, clamped color values +are kept in the hardware vertex, while texcoords remain in +ctx->Current. + +A crude diagram: + + +--------------+ +-------------------+ + | ctx->Current | | Current-HW-vertex | + +--------------+ +-------------------+ + \ / + \ / + \ / + \ / + --------- -------- + | | + v v + +--------+ +--------+ +--------+ +--------+ + | vert-0 | | vert-1 | | vert-2 | | vert-3 | + +--------+ +--------+ +--------+ +--------+ + | + | + v + + DMA + + +Here values from ctx->Current and current-HW-vertex are merged to +build vert-2, which is then dumped to hardware (DMA). A state machine +determines which vertex is built in turn, and how the vertices are +used to present primitives to hardware. These actions all occur +during a call to Vertex{234}f{v}. + +Each vert-n includes clip coordinates and a clipmask in addition to +the hardware (window) coordinates. This information allows clipping +to take place directly on these vertices, if need be. + +t_dd_imm_capi.h + + Color{34}{fub}{v}() implementations. These update both + ctx->Current (unclamped float colors) and current-HW-vertex + with hardware-specific color values (typically unsigned + bytes). + + When lighting is enabled, the functions from src/api_noop.c + should be used, which just update ctx->Current. (The + current-hw-vertex colors are produced from lighting, which is + keyed to Normal3f). + +t_dd_imm_vb.c + + Support functions for clipping and fallback. See + t_dd_imm_primtmp.h. + +t_dd_imm_napi.c +t_dd_imm_napi.h + + Versions of Normal3f{v} to perform lighting with one or more + infinite lights. Updates ctx->Current.Normal and the current + HW colors. + + When lighting is disabled, use the functions from api_noop.c + instead. + + +t_dd_imm_primtmp.h + + State machine to control emission of vertices and primitives + to hardware. Called indirectly from Vertex{234}f{v}. Capable + of supporting hardware strip and fan primitives, and of + decomposing to discreet primitives for clipping or fallback, + or where the native primitive is unavailable. + +t_dd_imm_tapi.h + + Implementations of TexCoord{v} and MultiTexCoord4f{v}ARB to + fire a callback when transitioning to projective texture. + Most drivers will need to change vertex format at this point, + some may need to enable a software rasterization fallback. + +t_dd_imm_vapi.h + + Implementations of Vertex{234}f{v}. These perform + transformation and cliptesting on their arguments, then jump + into the state machine implemented in primtmp.h. + +t_dd_imm_vertex.h + + Support functions for building and clip-interpolating hardware + vertices. Called from primtmp.h. + + +Keith Whitwell, June 2001.
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