Vertex displacement: tex2Dlod alternatives for GLES 2.0?

Hi all,

I'm using the volumetric explosion shader created by Steve Craeynest (full shader located here). The shader uses tex2Dlod to sample the displacement texture, and I've found this doesn't work on my android device (which is on GLES 2.0). From my research it seems tex2Dlod is not supported (bar using an extension). The troublesome code is below:

Code (CSharp):

1. void disp (inout appdata_full v)
2. {
3.     float3 dcolor = tex2Dlod (_DispTex, float4(v.texcoord.xy,0,0));
4.     float d = (dcolor.r*_ChannelFactor.r + dcolor.g*_ChannelFactor.g + dcolor.b*_ChannelFactor.b);
5.     v.vertex.xyz += v.normal * d * _Displacement;
6. }

Does anyone have any recommendations on how I can achieve a similar result without using tex2Dlod? I should note that I'm quite a shader novice so I really appreciate any help you can give, thanks.

 

Not sure what is going wrong, using:

Code (CSharp):

1. float4 dcolor = tex2D(_DispTex, v.texcoord.xy);

Getting error:

Edit:
I've found various posts that suggest that tex2D cannot be used for a vertex texture fetch - would that be why? Any other alternatives?

 

As far as I know, it's hardware support. The hardware, quite literally, does not support texture fetches in the vertex pipeline. Just keep in mind that GPU programming is vastly different from CPU programming.

And tex2D cannot be used for a texture fetch, because tex2D calculates the mip levels for the pixel, and the vertex doesn't have the information that is used to calculate the mip level, so you have to select a mip level manually (via tex2Dlod).

I'm fairly sure that what you want is not possible without rethinking the whole concept (not positive, but fairly sure), or by limiting it to higher end devices.

 

You could replace the texture lookup with a noise function, but this will likely be too slow unless your explosions only have a few verts. The other option is to animate the verts on the CPU.

 

I know this forum is already dead, but I'm just wondering. Is there any solution for using tex2Dlod for android? Or it's just unsupported for this platform?

 

Tex2DLod is supported on Android as long as the device supports GL ES 3.0. If you need to target older versions, there's no workaround other than what JBooth mentioned above. Note that if you want to read the texture on the CPU it will be a lot slower.

 

Step 1: Add

#pragma target 3.0

to your shader pass.
Step 2: Use

tex2Dlod()

in your vertex function.
Step 3: There is no step 3.

That “target” was originally the Shader Model version the shader needed to support. This is a little messy since OpenGL doesn’t adhere to explicit Shader Model versions as that’s a Direct3D thing, and there are no “half” versions. In fact Unity has no explicit OpenGL ES 2.0 target. Unity shaders default to

#pragma target 2.5

, which isn’t explicitly GLES 2.0, but rather “DX11 feature level 9.3” which was used on Windows Phone OS devices and is essentially OpenGL ES 2.0, but slightly worse, and is definitely worse than the Direct3D 9.0c that Unity supported on PC at the time. The problem is there’s a very wide range of features that “OpenGL ES 2.0” devices may or may not support. Some later OpenGL ES 2.0 devices might support

tex2Dlod()

without explicitly being fully GLES 3.0 compatible.

That

#pragma target 3.0

is Shader Model 3.0, which added

tex2Dlod()

support (among other things) and may, or may not run on OpenGL ES 2.0 devices depending on if it happens to support it or not.

If you need to allow the game to run on older OpenGL ES 2.0 devices, then the only practical option is to deform the mesh via C#.