[SOLVED] Distortion Shader Doesn't Work on Android Version

[PotatoDude]

Hello, this's my first post.

Ok, so the problem is:
I try so render a picture with distortion shader. It worked perfectly fine in the desktop version, but not in the android one. Any clue?

[ReFreezed]

Looks like the u coordinate is always 0 in the shader for some reason. Try returning the uv coordinates.

Code: Select all

vec4 effect(vec4 color, Image TEXTURE, vec2 uv, vec2 pc) {
    return vec4(uv, 0.0, 1.0);
}

Maybe try with a different image, possibly with power-of-two dimensions.

[PotatoDude]

Hey! Sorry for the late reply.

Looks like the u coordinate is always 0 in the shader for some reason. Try returning the uv coordinates.

Code: Select all

vec4 effect(vec4 color, Image TEXTURE, vec2 uv, vec2 pc) {
    return vec4(uv, 0.0, 1.0);
}

Yea, I just realized that in android version, it render the most left pixel only (I tried to use an image with a red dot on the mid left).

distort desktop version

desktop_version.jpg (40.93 KiB) Viewed 1972 times

distort android version

android_version.jpg (55.51 KiB) Viewed 1972 times

Unfortunately it's not the uv's problem; it's works just normal when I returning the uv coords.

uv test android version

android_uv.jpg (74.59 KiB) Viewed 1972 times

Maybe try with a different image, possibly with power-of-two dimensions.

Ok, I've changed the image to 256x256 res

[PotatoDude]

And this's the .love file. Idk but I can't add more than 3 attachments in a single post.

[PotatoDude]

I solved it!

The problem is rather simple tho
Based on the wiki:

On mobile devices, variables in pixel shaders use mediump (16 bit float) precision by default instead of 32 bit float, for performance reasons. This may cause numeric instability or visual artifacts for larger numbers. Use the highp qualifier when declaring a variable (for example highp float pos;) to make it use always 32 bit float precision. Furthermore, highp precision is not supported on all devices, particularly GLES2 devices. Use love.graphics.getSupported to check!

Basically in mobile device the float precision is set to mediump by default. And it's a problem since the noise generator function needs a highp precision.https://github.com/ashima/webgl-noise/wiki

You do not need a super fast GPU to use these functions. They are useful even on low end hardware, old hardware and embedded OpenGL ES hardware with low performance. However, they require support for "highp" precision.

For ones whose facing the same problem, here's the solution:

Code: Select all

precision highp float; //on top of the file

mediump vec4 effect(mediump vec4 color, Image TEXTURE, mediump vec2 uv, mediump vec2 pc) {
// your main code here
}

The precision highp float sets the precision to highp, but leave it alone will returns error at the love2d vec4 effect function. Set it and its arguments to mediump will solve it!

[ReFreezed]

I feel silly now. I'm using the same noise generator code from that very repo in my current project and I remember reading about the precision requirement. D'oh.

[PotatoDude]