How to replace a GLSL uniform array with a 1D texture

I am trying to get Ardor3D's terrain system to work on SM3.0 hardware.

The current GLSL fragment shader uses a uniform vec2 array to pass an array of xy coordinates into the fragment shader.

As dynamic indexed uniform arrays only work on SM4.0+ hardware, to get it running on SM3.0 I need to replace it with a 1D float texture.

The current array looks like this: uniform vec2 sl开发者_如何学编程iceOffset[8];

and is accessed like this: vec2 offset = sliceOffset[int(unit)];

I am very experienced with OpenGL and GLSL so I am having some problems doing the conversion.

So far I have done this: Create a 1D texture - width = 8 - format = RGBA32F

Create a 1D buffer for the texture

• width = 8 * 4 = 32 floats, or 32 * 4 = 32 bytes large
• fill the float buffer like this:

[x0,y0,0,0,x1,y1,0,0,x2,y2,0,0,x3,y3,0,0,x4,y4,0,0,x5,y5,0,0,x6,y6,0,0,x7,y7,0,0]

Create a 1D sampler for the texture

• min filter = nearest, no mip maps
• mag filter = nearest
• wrap mode = clamp to edge

In the GLSL I define the sampler as: uniform sampler1D sliceOffset;

And accesses it:

vec2 getSliceOffset(float unit)
{
 float texCoord = (unit * 2.0f + 1.0f) / (2.0f * 8.0f);
 vec2 offset = texture1D(sliceOffset, texCoord);
 return offset;
}

But it is broken.

What am I doing wrong?

Everything you're showing looks right. "It is broken" is not very descriptive though. What are the symptoms ?

Some things that you don't show that may be wrong:

• 2 samplers using the same texture unit.
• type issues in the texture data (although if you're experienced, I doubt it)

One additional thing you could try: use a texture2d instead, with just height=1. DX does not require 1d texture support, so depending on hardware, the opengl support for it might be emulated. You can try to stay away from such emulation.

The texCoord calculation is correct. It was confusing at first since I would've done (unit + .5) / 8.0, but it's the same.

One thing still worries me though. Don't you need to write .rg at the end of your sampler statement since the texFetch will be a vec4? I'm surprised that your compiler isn't complaining about it.

Try:

texture1D(sliceOffset, texCoord).rg;