Unity: Render 1st Texture to 2nd Texture

Question

I want to pass the first texture through a shader and render it to a second texture.

The actual task is bit more complicated, as I then want to render the second texture back to the first texture also using a shader.

I have a terrible solution at the moment involving two cameras, two quads and two materials and two rendertextures. The output of Cam1 is rendered to Texture1 used in Material1 applied to Quad1. Quad1 is in the view of Cam2 rendered to Texture2 used by Material2 applied to Quad2. Quad2 is of course in the view of Cam1. I then have to alternate turning on and off the Cameras and the Quads. It works, but the solution is terribly complicated.

Please tell me there is a better solution. With WebGL I could do this simply by swapping source and target for the shader. I'm sure this can be done in Unity too, but I have no clue what to look for.

Answer 1

Turns out it's simple, if you get great advice from DMGregory.

Graphics.Blit(sourceRenderTexture, targetRenderTexture, unlitMaterial, -1);

is the answer. I'm using an Unlit Material with Shader and that's it. If you need to set a sprite to your rendertexture, this also works with Blit

Graphics.Blit(sprite.texture, renderTexture);