On 03/05/2012 10:54 AM, Ethan Fahy wrote:
If I were to set the color of a vertex of an osg::Node using floats between 0-1
and then accessed the color of that same vertex in a GLSL shader, would I get
back the exact same floating point value? I am worried that at some point in
the pipeline that float would be scaled to an 8 bit unsigned int between 0-255
and then rescaled back to a 0-1 float when accessed using GLSL. The reason I
ask is that I am hoping to use the floating point value to carry a scaled index
number for a lookup table in the shader instead of a color, so precision would
be important.
Hi, Ethan,
If you're talking about vertex attribute data, you're likely get the
same value back that you originally specified. The vertex attributes
will remain in float form until you actually rasterize the vertices.
Only at that point will they need to be converted to fit the data format
of the framebuffer.
That said, it's generally not a good idea to rely on floating point
values to be exactly the same from one call to the next. I'd recommend
trying to come up with a different way to do what you're attempting, or
at least use an epsilon value in your comparison.
--"J"
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