Calling "clear" on RenderTexture « cocos2d for iPhone

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Calling "clear" on RenderTexture

(9 posts) (4 voices)

Started 2 years ago by Receptor
Latest reply from slipster216

Tags:

draw

Receptor
Member

Hi,

this might be a bug, but before creating an issue I wanted to be sure it's not just me.

I have a layer and in the init of it I create a RenderTexture instance
RenderTexture *rt = [RenderTexture renderTextureWithWidth:100 height:32];

then I just call clear on it:
[rt clear:100 g:100 b:100 a:255];

and the WHOLE background becomes WHITE (not even gray as per passed RGB values).

The instance is not even attached to the layer.
I did few tests and that's what I found out:
- if I add the RenderTexture instance to the layer, I can see that the texture is actually cleared, but just in white
- it doesn't matter if the instance is attached to a layer, the whole layer's background becomes white
- if I don't clear and I just call begin, then draw something and then end... everything works (until the next clear)

I'm using Cocos2d 0.8.1 with SDK 3.1.2, tested both on simulator and on a iPhone 3G (same thing)

Any idea?

Posted 2 years ago #
Steve Oldmeadow
Administrator
Try
```
[rt clear:0.4f g:0.4f b:0.4f a:1.0f];
```
Posted 2 years ago #
Receptor
Member

Hi Steve,

you're right, I didn't see the arguments were floats.
But... it doesn't work anyway!
Well, now the color is right, but still the whole layer's background (or maybe it's the window's background, I'm not sure) becomes gray.

The wrong numbers I used earlier couldn't cause it anyway, because OpenGL probably just truncates them at 1.0f (that's why everything was white).

Can anyone test it?

Posted 2 years ago #
Receptor
Member
Ok I did a very very simple test.
I created a new project using the Cocos2d Application template (I'm using 0.8.1).
Then in HelloWorldScene.m, at the end of the init method of the layer, just after [self addChild:label], I added the following:
```
RenderTexture *rt = [RenderTexture renderTextureWithWidth:128 height:128];
 [rt clear:0.3f g:0.4f b:0.5f a:1];
```
That's it. The node is not even attached to the layer. And it's supposed to be 128x128.
But when I run it (debug, release, simulator or device) the whole background becomes grayish (as per arguments).

Either I didn't understand anything about RenderTexture, or this just doesn't work.

Can anyone do this small test? It takes 3 minutes.

Thanks!
Posted 2 years ago #
CJ
Moderator
I'm pretty sure you would want to do a begin/end around that clear or it will actually affect your current framebuffer.

example:
```
[rt begin];
[rt clear:0.3f g:0.4f b:0.5f a:1.0f];
[rt end];
```
This way it's only clearing the render texture's framebuffer.
Posted 2 years ago #

Receptor
Member

No, it's calling begin and end by itself. This is an extract of the source code from RenderTexture.m:

-(void)clear:(float)r g:(float)g b:(float)b a:(float)a
{
	[self begin];
	glColorMask(TRUE, TRUE, TRUE, TRUE);
	glClearColor(r, g, b, a);
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glColorMask(TRUE, TRUE, TRUE, FALSE);
	[self end];
}

And actually it is clearing the render texture's framebuffer, but ALSO the whole background.

Posted 2 years ago #

Steve Oldmeadow
Administrator
glClearColor sets the clear color for all clears and the Director calls glClear every frame. Therefore just restore the clear color after you've cleared the render texture.
```
[rt clear:0.3f g:0.4f b:0.5f a:1.0f];
glClearColor(0.0f,0.0f,0.0f,1.0f);
```
Posted 2 years ago #
Receptor
Member

I see, that explains everything. Thank you Steve.
Shouldn't the RenderTexture class take care of this anyway?
Maybe a call to glGet to retrieve the color values before changing it, and then restoring the original ones.

Thanks again!

Posted 2 years ago #
slipster216
Moderator

Yeah, it should - feel free to submit a patch for this..

Posted 2 years ago #

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