[Public WebGL] Shaders, glReadPixels and speed
Sun Jan 3 21:00:06 PST 2010
On 04/01/2010, at 5:24 AM, Kenneth Russell wrote:
> What browser and operating system are you using? Safari on Mac OS X
Mac OS X 10.5, which probably lacks the hardware composition in the
browser (despite being nightly). It is good to know that all browsers
are moving towards hardware compositing to address this bottleneck.
> needed but the raw speed of sending down floating point numbers via
> WebGLFloatArray is already pretty good.
I was referring more to the step by step nature of needing to feed
variables through, which leads to this kind of analysis:
Gregg Tavares <[email protected]> writes:
>> 1 call to for each matrix you want to pass to the shader (usually 1
>> to 4 matrices)
>> 1 call for each color parameter ( for phong the minimum would be 2,
>> and shininess though most phong shaders have 5, emissive, ambient,
>> specular, shininess)
>> 1 call to setup position vertices
>> 1 call to setup normals
>> If it's textured you'll need another call to supply UVs
>> 1 call to finally draw the object
>> and then possibly a few calls to restore GL state.
>> That a minimum of 5 calls and in this case a maximum of 13 per
>> object, per
>> than a
>> few objects and keep 60 or even 30hz.
Rather than having a custom engine like O3D, it seems less
controversial to add in a standard GL_ARB_geometry_shader4 so that
WebGL is capable of displaying and animating 3d graphics to an
The shaders have the vector and matrix functionality that is a painful
that domain? Use a fragment shader and render vertex data to a texture?
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