I’m diving into using shaders with Phaser and I hit a bit of a wall. My goal is to blend a noise texture onto a specific image or sprite, but what actually happens is that the noise gets applied to the entire canvas instead—definitely not what I’m aiming for!
I’ve set up a basic example where I create a circular image (`circle_triangles`) and then I define a shader that I want to use to apply the noise texture. Here’s a slice of the code I’ve prepared:
“`javascript
const circle = this.add.image(300, 300, ‘circle_triangles’);
const base = new Phaser.Display.BaseShader(‘water’, frag);
const shader = this.make.shader({key:base});
shader.setChannel0(‘nnnoise’);
circle.postFX.add(shader);
“`
The intent was to use the noise texture as a post-processing effect just for that circle image, but as you’ll see if you check out my sandbox example (link below), the noise covers the whole screen instead. It’s frustrating because I can see the effect looks cool, but it’s just not localized to the image.
I’ve attached an example image to give an idea of what I’m trying to achieve—basically, I want the noise effect to only apply onto the image of the circle itself, not bleed over into the rest of the canvas. I thought using `circle.postFX.add(shader);` would do the trick, but it seems like the shader is acting on the entire render target.
If anyone has experience with Phaser’s post-processing effects, especially with shaders, I’d really appreciate any advice or insights! Maybe I’m missing a step or a specific configuration to keep the shader’s effects localized. I want to capture that cool, glitchy vibe but only on my circle image!
Here’s the link to my sandbox example for a better look at what’s happening: [Phaser Sandbox Example](https://phaser.io/sandbox/kps95sUs). Any tips, tricks, or pointers on how to fix this would be super helpful. Thanks a lot!
It sounds like you’re really close to getting that cool noise effect localized to your circle image! From what you’ve described, it seems like the issue might be due to how the shader is applied. When you use `circle.postFX.add(shader);`, it typically applies the shader to the whole canvas if the shader isn’t specifically set up to limit its effect to just the circle.
Here are a few things you could try:
Also, when you test your changes, make sure to restart the scene or clear the previous shader effects to see the changes properly. It can be a bit trial and error, but getting that localized effect with shaders is definitely achievable!
Good luck with your Phaser project, and I hope you get that glitchy vibe just where you want it!
When using shaders with Phaser’s post-processing effects (such as
postFX.add()), you’re actually applying the shader to the entire framebuffer or render target by default, rather than a single sprite. This explains why your noise effect affects the entire canvas instead of just the specific image. To localize this shader effect to only the circle image, you’ll need to make a couple adjustments: first, ensure your shader fragments utilize the sprite’s UV coordinates and alpha channels correctly, and second, explicitly limit the shader’s output to affect only the desired sprite shape.A practical solution is to use a RenderTexture or a custom pipeline. For instance, you can create a RenderTexture, draw your sprite on it, then apply your shader effect directly onto that RenderTexture. Alternatively, crafting a custom shader pipeline (instead of postFX) gives you full control over the attributes and uniforms, enabling you to directly reference the sprite’s texture and correctly restrict the effect to the sprite boundaries. These approaches let you precisely contain the noise effect within your sprite, achieving the glitchy vibe you’re aiming for without affecting the entire canvas.