Retrieving alpha from framebuffer

[Epihaius]

@rdb

This turned out to be a bug, to which I just checked in a fix.

Ah, great, thank you!

@rdb

However, it had nothing to do with the use of PNMImage or TexturePeeker. What was different in your code snippets is that in the PNMImage case you called set_float_color(True), which triggered different logic that didn’t suffer from the same bug.

As for r32g32b32a32 buffers being more expensive than r8g8b8a8 buffers: it’s just about texture bandwidth, but I suppose that doesn’t really matter if you’ve only got one pixel.

Thank you for the explanations .

@geofurb

Novice programmer here, hoping to learn. Can you explain what you mean by trying to detect objects and a picking camera?

In my project, Panda3D Studio (shameless plug ), you can manipulate model objects (and their subobjects), but to do so, you need to select them first. Instead of having to choose an object’s name from a list, it’s obviously more intuitive and user-friendly to be able to just click on the object. Collision detection could be used for this, but is far too slow when many objects need to be checked. Instead, I prefer a technique called “picking”; basically, each object is rendered a second time, with a unique color. This color can then be retrieved from the framebuffer to identify the object the mouse is over. Normally, this could also be slow, depending on the window size, but I use a trick: I create a special “picking camera” to render only the exact pixel that the mouse is currently over, so it’s quite fast.