The rendering results of projected textures vary with different resolutions.

[394452216@qq.com]

A: 1000X1000
B: 3500X3500
Corona 12 update 1

[394452216@qq.com]

Render B

[romullus]

That is expected behaviour. Blur in 3ds Max is used to avoid aliasing, its results depends on texture size in rendered image - the smaller texture will be, the more it will be blurred. If you want that blurring would stay constant independently on texture's size, you need to use blur offset, not the blur. You can read about this in Max's documentation: https://help.autodesk.com/view/3DSMAX/2024/ENU/?guid=GUID-8AE3643F-BDB4-498B-B220-92646FC8A562

[pokoy]

If this is about map filtering, it is expected but certainly not the degree visible here.

However, it looks to me like this is about texture from a light (gobo), or shadows cast through some tree-like geometry above, right? Not a texture in a material on an object.

If that's the case, it's probably due to the fact that Corona resizes environment maps (both HDR maps and Corona's Sky&Sun) internally. The default value works for most cases, can however result in blocky artefacts from the sun which would look exactly like what's happening here.

The solution is to use this in the string options window in the render dialog window (development/experimental stuff), restart the render if you're updating this while in IR:
int lights.envResolution = 4000
 
AFAIK the default valuue is 1000, try 2000, 4000 or some other value that improves the shadows. Keep in mind it will take longer to render and might result in a noisier image.

[pokoy]

Just to add this: IF the issue is blocky shadows, I found a thread that reports this with some discussion on the topic and the solution (same one I posted above).