[Public WebGL] Shaders, glReadPixels and speed
Sun Jan 3 04:51:59 PST 2010
I am finding that WebGL has a per pixel performance that is amazing,
but a per item performance that is very slow. The speed between the
vertex and fragment shaders is unhampered, but things bog down in two
* Transferring graphics back to the browser instead of drawing
directly to screen. This makes a full screen 30x30 textured sphere
slower than the same thing in Flash set to wmode=opaque. WebGL needs
an equivalent wmode.
card variable by variable. The maths is optimised by the JIT, but the
bridging cost is too large to help by having a C based implementation.
PROPOSAL: WebGL needs to specify a geometry shader API, with a
fallback software implementation as a requirement.
I know geometry shaders are not in OpenGL ES, however there is a
increased emphasis on the need for geometry shaders as a result of
does not have that luxury, therefore it needs geometry shaders.
Geometry shaders can be mostly implemented with vertex/fragment
shaders, so the overhead would be minimised on platforms without
hardware support. The flexibility of geometry shaders also forms the
basis for writing hardware accelerated scenegraph engines, which would
be WebGL's answer to Google's O3D and their amazing island.
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