V4.0 glsl-optimizer for Metal and some other issues

cocos2d-x C++
#1

Hi,

I wanted to reply to this thread but unfortunately it’s closed :frowning:
https://discuss.cocos2d-x.org/t/are-you-using-v4-metal-currently/47145/48

Anw, thank you cocos2d-x team for bringing Metal support in v4.0! I have been using it and it works fine out of the box.
However, i have bump into an issue with my custom shaders. For example in this code snippet.

void main()
{
    v_fragmentColor = a_color;
    v_texCoord = a_texCoord;

    vec2 flowDir = vec2(texture2D(u_flowTexture, a_texCoord).rg);
    .
    .
    .
    vec4 pos = a_position;
    pos.xy -= flowDir * u_time;
    gl_Position = u_MVPMatrix * pos;
}

After going through the glsl-optimiser, the vec2 flowDir is swapped with a type of half4 instead of float4. And since gl_Position underwent some operation with vec4 pos, which underwent an operation with flowDir, this resulted in gl_Position being declared as a half4 and not float4 and this will cause the Metal shader to fail to compile because vertex shader has to return a float4 gl_Position.

Basically, if the gl_Position is calculated from anything that derives from a variable that derives from a half, it will have the precision reduced to half instead of float. And I notice that anything that results from texture2D operation always result in a half.

Has anybody came across this issue and found a solution for it?

I had a temporary fix for this on a leaner project, whereby I have a separate file for the Metal shader that I manually corrected the variable type. But I had to perform some edit to the engine’s renderer codes so that it takes in a separate file.
But I don’t think this is a viable solution when it comes to a big project. The ideal case is to manage just 1 file for each shader instead of having to manage different shader language versions of it.

V.4 Shaders. Create a ProgramState?
#2

I’m a new user of the v4.0 GLSL-optimizer based on Cocos2D-x, I can’t figure out why I use GLSL3.00, it works, but when I use GLSL1.00, ’ const char* metalShader = glslopt_get_output(glslShader);’ will return null, while ’ glslopt_shader* glslShader = glslopt_optimize(mCompilier, shaderType, mSource.c_str(), 0);’ is always works.

#3

Hi @liangzi10101, you have any code snippet to show how do you set GLSL1.00 or 3.00 in code?
and in what ocassion do you need GLSL1.00? How about just use OpenGL 2?

#4

Actually, I just use glsl-optimizer like this:

mCompilier = glslopt_initialize(kGlslTargetMetal);
glslopt_shader_type shaderType = mType == GFXShaderType::Vertex ?
kGlslOptShaderVertex : kGlslOptShaderFragment;

glslopt_shader* glslShader = glslopt_optimize(mCompilier, shaderType, mResult.data(), 0);
if (glslShader) {
    const char* metalShader = glslopt_get_output(glslShader);
    if (!metalShader) {
        NSLog(@"[Shader Error] : Can not get metal shader:\n");
        return Status::Error;
    }
}

So, metalShader is NULL when ‘mResult.data()’ is GLSL1.00, but it can work when ‘mResult.data()’ change to GLSL3.00, T_T.
The occassion is I want to use GLSL1.00 to match the standard of WebGL1

#5

Hmm… i’ve been using glsl #version 100 shaders from cocos2d-x and there is no problem.
Is there any error message?
And when you change from 3.00 to 1.00, did you change the in / out to attributes / varying ?