I've hit a road block in the development of my OpenGL renderer regarding the size of point sprites. I have been writing the features of my renderers for DirectX first and then I immediately port them to OpenGL after I get them working, since Windows is my primary platform and DirectX seems to be easier to write for (come get it haters lol). I noticed that you can't set the point size for each point sprite individually in OpenGL as you can in DirectX (and OpenGLES), unless you use a shader. My readings tell me that I can cheat using the Z value and distance attenuation to achieve the same effect. My question is how do I use this to make my point sprites look exactly the same in OpenGL as they would in DirectX? I trying to avoid taking the shader route for this because I want my engine to be able to run on older hardware.

<blockquote class='ipsBlockquote'data-author="mhagain" data-cid="5013381" data-time="1356177245"><p>
<blockquote class='ipsBlockquote'data-author="justin12343" data-cid="5013246" data-time="1356124157"><p><br />
I trying to avoid taking the shader route for this because I want my engine to be able to run on older hardware.</p></blockquote>
Not a direct answer to your question, but I'd strongly urge you to reconsider this. The reason why is: it's now 2012, shaders have been available for over a decade, so: older hardware supports shaders too. In fact, <a href='http://en.wikipedia.org/wiki/OpenGL#OpenGL_2.0'>point sprites are an OpenGL 2.0 feature, and OpenGL 2.0 includes shader support, so if you have support for point sprites then you also have support for shaders</a>.</p></blockquote>

Then I guess I'll be taking the shader route. Thanks for the reply!