Comments on: Stenciling for “deferred” lighting http://adruab.net/?p=80 Deep internal/external searching... for... stuff Mon, 13 Jul 2009 00:22:07 -0400 http://wordpress.org/?v=2.8.6 hourly 1 By: adruab http://adruab.net/?p=80&cpage=1#comment-65047 adruab Mon, 13 Jul 2009 00:22:07 +0000 http://adruab.net/?p=80#comment-65047 And actually come to think of it you might still be able to do single mad by computing the following in the vertex shader: ProjectToFarPlane(posWorld - posCamera). There may be issues with correct interpolation for geometry clipping through near/far, but you might be able to get around that with trickery. And actually come to think of it you might still be able to do single mad by computing the following in the vertex shader: ProjectToFarPlane(posWorld – posCamera). There may be issues with correct interpolation for geometry clipping through near/far, but you might be able to get around that with trickery.

]]> By: adruab http://adruab.net/?p=80&cpage=1#comment-64992 adruab Fri, 10 Jul 2009 03:22:57 +0000 http://adruab.net/?p=80#comment-64992 We read directly from the depth buffer and thus don't have linear z :). 3 components of the reverse projection matrix can be factored into the vertex shader, so you do perspective space Z * matClipToWorld[2] + vecXYW (float4 interpolated from vertex shader). Then you have a divide (recip + mul). So yes, it's 3 instructions and 1 interpolant instead of 1-2, but you don't have to store linear Z (full screen worth of RAM). Reconstructing perspective Z rather than sampling from a globally stored linear Z buffer, takes 3 instructions itself (on the RSX at least). I think a better argument for screen space tiles than saving a few arithmetic instructions is merging multiple lights to reduce (and potentially maximize cache reuse) for sampling giant textures. We'll probably try tiles again. However, stencil culling still feels like potentially anti-useful trade off. We read directly from the depth buffer and thus don’t have linear z :) . 3 components of the reverse projection matrix can be factored into the vertex shader, so you do perspective space Z * matClipToWorld[2] + vecXYW (float4 interpolated from vertex shader). Then you have a divide (recip + mul). So yes, it’s 3 instructions and 1 interpolant instead of 1-2, but you don’t have to store linear Z (full screen worth of RAM). Reconstructing perspective Z rather than sampling from a globally stored linear Z buffer, takes 3 instructions itself (on the RSX at least). I think a better argument for screen space tiles than saving a few arithmetic instructions is merging multiple lights to reduce (and potentially maximize cache reuse) for sampling giant textures. We’ll probably try tiles again. However, stencil culling still feels like potentially anti-useful trade off.

]]> By: JSeb http://adruab.net/?p=80&cpage=1#comment-64535 JSeb Tue, 30 Jun 2009 14:55:53 +0000 http://adruab.net/?p=80#comment-64535 Hi, I think you forgot one "con" for the alternate approach: some arithmetics of position reconstruction can be move to vertex part, but only when you render a full quad. (in pixel pipe, you can reconstruct position from linear_z with only a mad and 2 interpolants) When you render a bounding geometry, the position reconstruction can no longer be prepared in vertex space. Hi,

I think you forgot one “con” for the alternate approach:
some arithmetics of position reconstruction can be move to vertex part, but only when you render a full quad.
(in pixel pipe, you can reconstruct position from linear_z with only a mad and 2 interpolants)

When you render a bounding geometry, the position reconstruction can no longer be prepared in vertex space.

]]> By: realtimecollisiondetection.net - the blog » Catching up (part 2) http://adruab.net/?p=80&cpage=1#comment-64039 realtimecollisiondetection.net - the blog » Catching up (part 2) Mon, 08 Jun 2009 08:52:23 +0000 http://adruab.net/?p=80#comment-64039 [...] (re-)reading. And on the topic of deferred lighting, Adrian Bentley talks about the (non-)use of stenciling to accelerate same. Lastly, Adrian Stone makes an argument for deferred shading and against [...] [...] (re-)reading. And on the topic of deferred lighting, Adrian Bentley talks about the (non-)use of stenciling to accelerate same. Lastly, Adrian Stone makes an argument for deferred shading and against [...]

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