+1 vote

I have the following canvas item shader code. The problem with it is that rotation seems to speed up over time. I suspect this is caused by me also offsetting the UV over time. Im looking for way around this. Here is my code:

shader_type canvas_item;

uniform float rotation;
uniform float speed_scale;

vec2 rotateUV(vec2 uv, vec2 pivot, float rot) {
    float cosa = cos(rot);
    float sina = sin(rot);
    uv -= pivot;
    return vec2(
        cosa * uv.x - sina * uv.y,
        cosa * uv.y + sina * uv.x 
    ) + pivot;

void vertex() {
    UV.y += time * speed_scale;


void fragment(){
    vec4 color;
    color = texture(TEXTURE, rotateUV(UV, vec2(0.5), rotation ));
    COLOR = color;
in Engine by (20 points)
edited by

you are creating some kind of spiral function
what are you trying to achieve?

1 Answer

+1 vote
Best answer

This doesn't build, because of time. I'm only able to assume you were using TIME.

The first possible issue is in the way you're using TIME. TIME doesn't return a delta, it accumulates itself. It's total time elapsed. TIME


x += 10 * scale
x += 20 * scale
x += 30 * scale

Another possible problem is that you'll usually need to wrap the results for UVs when using TIME, otherwise it'll keep growing.

Simple example using mod:

COLOR = texture(TEXTURE, UV + vec2(0.0, mod(TIME, 2.0) - 1.0));
by (5,192 points)
selected by
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