sokol_gfx.h : resizing render targets (sg_image)

[siavashserver]

Hello! I was wondering how would one scale down render targets? (for effects like bloom)

[floooh]

To resize render targets with window size changes, you need to destroy and recreate them, along with their pass. Here's an example which recreates offscreen render targets when the sokol_app.h RESIZED event is sent:

https://github.com/floooh/sokol-samples/blob/7df270a9ed402af95f3560fecc74fef55174ddd1/sapp/mrt-sapp.c#L52-L100

The actual downscaling must be done with a pixel shader by rendering a fullscreen quad, there's no "fixed function" blitting operation in sokol-gfx.

[siavashserver]

Thank you!

On Thu, Jun 6, 2019 at 5:54 PM Andre Weissflog [e-mail]
wrote:

To resize render targets with window size changes, you need to destroy and
recreate them, along with their pass. Here's an example which recreates
offscreen render targets when the sokol_app.h RESIZED event is sent:

https://github.com/floooh/sokol-samples/blob/7df270a9ed402af95f3560fecc74fef55174ddd1/sapp/mrt-sapp.c#L52-L100

The actual downscaling must be done by rendering via pixel shader by
rendering a fullscreen quad, there's no "fixed function" blitting operation
in sokol-gfx.

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[siavashserver]

Forgot to ask, is it a webgl/opengles limitation?

[floooh]

No, WebGL is fine since it has a scaling glBlitFramebuffer function (I'm using this - without the scaling - to resolve MSAA render targets to textures in sg_end_pass().

The problem are the other APIs, both D3D11 and Metal only offer fairly limited copying between texture resources without scaling, so a full render pass is needed for this anyway (and it's also more flexible since you have better control over the scaling via the pixel shader).

[floooh]

...oops correction, WebGL doesn't have glBlitFramebuffer() that's a WebGL2 feature (that's why sokol_gfx.h doesn't support MSAA render target in WebGL(1).

So yeah, in addition to D3D11 and Metal, WebGL/GLES2 also wouldn't work :)

[siavashserver]

I wasn't aware that limitation applies to D3D11 and Metal as well. Thanks again :)