No blend mode.

[ljdp]

Is there a way to have no blending.
For example you have a group of shapes overlapping each other and you set a transparent colour
and they all become transparent (so they look like one single object)

overlappingshapes.JPG (2.55 KiB) Viewed 7893 times

If you look at that there are 4 circles and 5 rectangles, but they overlap so you can see the seperate objects.
I want them to look like one object.

[Robin]

I think you could try drawing the background first, next the shapes with 100% alpha, and then the background again with a lower alpha. I have no idea whether this actually works.

[rude]

You want the union of the two shapes to act as one transparent object?

EDIT: Rephrased.

[ljdp]

Yes, what rude said.

[rude]

I wonder if this is possible with glBlendFunc at all. Hmm, I don't think it can be combined with normal blending (transparency).

Might need to implement render targets for this.

[ljdp]

Well I don't really know how blending works.
But I assume it takes each pixel of an object and does some math between the values.
Can't you just say

Code: Select all

if object1Color == object2Color then
     finalColor = object1Color
end

[Robin]

If you're interested: my hack works. I've added a small example.

[ljdp]

Nice!

EDIT: lol, looking at your code it never occured to me you only needed to draw 2 rectangles for a rounded box i've been drawing 5

[Robin]

(...) you only needed to draw 2 rectangles for a rounded box i've been drawing 5

yeah

The bad news is: my hack is a bit limited. It's hard to have objects of different transparencies (you could of course add layer on top of layer, but then you can't choose the drawing order yourself), and a completely opaque shape is always on the foreground. Unless you make it part of the background, in which case you have to draw everything at least twice.

I think the best solution would be to allow drawing to off-screen buffers, and blitting them later, with optional transparency.

[osgeld]

I think the best solution would be to allow drawing to off-screen buffers, and blitting them later, with optional transparency.

This is one of the things i miss most with love, its just so darn useful for so many things