Blend modes are not set on WebGL Graphics primitives drawn to a RenderTexture

[danarcher]

Version

• Phaser Version: v3.52.0
• Operating system: Windows 10 Version 1909 (OS Build 18363.1379)
• Browser: Firefox 85.0.2 (64-bit)

Description

Under WebGL, calling setBlendMode() on a Graphics object has no effect when drawing that Graphics object to a RenderTexture.

The workaround is to add the Graphics object to a Container, and draw that Container to the RenderTexture.

This came up whilst drawing primitives to a Graphics object using additive blending, then drawing that RenderTexture to the scene using multiplicative blending, in order to implement a light/shadow effect.

Example Test Code

See https://codepen.io/danarcher/pen/OJbWYeW. The code is drawing concentric circles using additive blending.

Set workaround to true to see the workaround in effect, whereby concentric circles of increasing (additive) brightness are visible.

The workaround isn't necessary when using the canvas rather than WebGL renderer (change Phaser.WEBGL to Phaser.CANVAS in the example to demonstrate).

Additional Information

There is no call to the renderer to set the blend mode from GraphicsWebGLRenderer or RenderTextureWebGLRenderer.

There is a call to the renderer to set the blend mode from ContainerWebGLRenderer.

[sjb933]

I can confirm I'm experiencing the same issue. In my game I handle dynamic lighting and shadow casting with some shader tricks:

1. I draw each light source to a RenderTexture with, taking into account occlusion and shadow casting from game objects.
2. I apply a fragment shader to this for soft shadows and light fade
3. I draw each individual light source RenderTexture from step 1 to a composite lighting render texture with additive blending
4. I draw the composite lighting RenderTexture to my scene with multiplicative blending.

What I'm experiencing is very similar to the reported issue here - that the additive blending of my light maps isn't working when targeting my composite light map RenderTexture. Using WebGL

[photonstorm]

Thank you for submitting this issue. We have fixed this and the fix has been pushed to the master branch. It will be part of the next release. If you get time to build and test it for yourself we would appreciate that.