Updating shader uniforms for animated effects

[Mike Clifton]

I'm working with a SkRuntimeShaderBuilder object, and I want to update the values of some uniforms over time for an animated effect. To create the actual shader to use with the SkPaint object, I call SkRuntimeShaderBuilder::makeShader

It seems I need to call SkRuntimeShaderBuilder::makeShader whenever I change the values of the uniforms, and then I use that new shader. When I do this, it all appears to work as expected, but I want to make sure I'm not doing something horribly inefficient.

Is it appropriate to maintain the same SkRuntimeShaderBuilder object, modify its uniforms, and then call makeShader over and over again? If I try to re-use the result of makeShader to be more efficient, I'm not sure how to change the values of the uniforms.

[John Stiles]

You're doing it properly. This should be efficient. 

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[Brian Osman]

Yeah, you're using it right. Many Skia objects (like SkShader) are immutable - once created, they're set in stone. In this case, most of the information about the shader is actually stored on the SkRuntimeEffect (and that's held by reference), so the only thing being copied each time is basically the updated values for all the uniforms - makeShader just creates a snapshot of the uniform and child data.

On Sat, Mar 30, 2024 at 8:59 AM Mike Clifton <mike.o....@gmail.com> wrote:

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[Mike Clifton]

Awesome - thanks!