ofClear uses inconsistent arguments

[kylemcdonald]

ofClear(r,g,b) is inconsistent with ofBackground(r,g,b) because the alpha is 0 by default -- meaning you always have to explicitly declare the alpha to clear the background.

furthermore, because all the arguments have default values there is not/cannot exist an ofClear(gray, alpha) to match ofSetColor style

[memoakten]

I agree ofBackground and ofClear should be consistent in their default values (actually I find ofBackground to be a very confusing function name, it should probably be ofSetBackgroundColor).

But I think default alpha should be 0 (for both). By default the window and glview are opaque, so in most cases it makes no difference. However if you draw to an fbo, you probably want the places where you aren't drawing to to be transparent, UNLESS you explicitly fill it with a solid color.

[kylemcdonald]

i just want to chime in again and say i think this is still a bug in my opinion.

i was writing some code with ofFbo and ofClear() and everything was going well until i enabled alpha blending -- and then the background "stopped clearing". it took me a while to remember that it's because ofClear() uses a transparent black by default, not an opaque one. very confusing in my opinion for the behavior of clear to change just by enabling blending.

[memoakten]

Hm interesting one. To me that sounds normal.

Enable blending.
You start an fbo.
Clear it
Draw a red circle in the Center.
End the fbo.
Draw a bunch of random shapes to screen.
Draw the fbo to screen.

Youd expect to see the random shapes on screen and the red circle on top
right? If ofclear cleared to alpha==1 by default then the fbo wouldn't be
transparent, you wouldn't see the random shapes, just black. Of course
enabling blending changes the behaviour of how the fbo is drawn, ignoring or
not ignoring the alpha! :)

Just my 2p

On Monday, 19 September 2011, Kyle McDonald <
reply@reply.github.com>
wrote:

i just want to chime in again and say i think this is still a bug in my
opinion.

i was writing some code with ofFbo and ofClear() and everything was going
well until i enabled alpha blending -- and then the background "stopped
clearing". it took me a while to remember that it's because ofClear() uses a
transparent black by default, not an opaque one. very confusing in my
opinion for the behavior of clear to change just by enabling blending.

Reply to this email directly or view it on GitHub:

#264 (comment)

Memo Akten
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+44 20 8123 9986

[kylemcdonald]

i understand your usage (i use fbos like that sometimes too), but i don't see it as the default. for me, saying this:

drawStuff();

should always have the same behavior as this:

fbo.begin();
drawStuff();
fbo.end();
fbo.draw(0, 0);

and if drawStuff() contains ofClear(0) then this intuition does not necessarily hold right now.

but that's just my intuition, and you're the one who wrote ofFbo ;) it would be good to get some other opinions on this.

[memoakten]

definitely get other opinions, but if blending is enabled I wouldn't expect
the same results. Of course within the fbo you can get the same results, but
when that fbo is drawn to screen you'd get different results.

The way it's setup an FBO works the same way as a PNG. If you load a PNG of
a red circle and transparency around it, it will look different if blending
is enabled or disabled.

Memo Akten
www.memo.tv
www.twitter.com/memotv
+44 7958 783 832

The Mega Super Awesome Visuals Company
www.msavisuals.com
Unit 107 Netil House
1 Westgate Street
London E8 3RL, UK
+44 20 8123 9986

On 19 September 2011 09:26, Kyle McDonald <
reply@reply.github.com>wrote:

i understand your usage (i use fbos like that sometimes too), but i don't
see it as the default. for me, saying this:

   drawStuff();

should always have the same behavior as this:

   fbo.begin();
   drawStuff();
   fbo.end();
   fbo.draw(0, 0);

and if drawStuff() contains ofClear(0) then this intuition does not
necessarily hold right now.

but that's just my intuition, and you're the one who wrote ofFbo ;) it
would be good to get some other opinions on this.

Reply to this email directly or view it on GitHub:

#264 (comment)

[julapy]

was about to log an issue for this very same thing when i remembered you guys chatting about this.

i found it very confusing that ofClear(255) clears the fbo and makes it transparent.
when i think ofClear, it is like filling the fbo with a color value.
so writing ofClear(255) should make the fbo white.
on the other hand, ofClear(255, 0) should make the fbo transparent.
this is in line with the way ofColor class works.

+1 for making ofClear always default to opaque.

required changes below.

void ofClear(float r, float g, float b, float a=255);
in https://github.com/openframeworks/openFrameworks/blob/master/libs/openFrameworks/graphics/ofGraphics.h#L243

void ofClear(float brightness, float a=255);
in https://github.com/openframeworks/openFrameworks/blob/master/libs/openFrameworks/graphics/ofGraphics.h#L254

[tgfrerer]

Related #3566

[oxillo]

Hi,

We are trying to clean out the many issues that we have.
Many versions of OF have been released since this was issued.

Can you help us by checking if this issue is still present in the latest version ?

In case of inactivity, we'll close this issue by end of january, 2020.

Thanks