annoying cosmetic texture problem.

Member
Posts: 321
Joined: 2004.10
Post: #1
This is the mother of all irritations and I've been trying to solve it off and on
again for over a year and after another recent unsuccessful session I thought
{ glEnable(SHAMELESS_BUTTER_UP_MODE) } the incredibly knowledgable
people on this forum might have some suggestions or ideas.

I've got a blue sceen with a white RGBA texture (targa, 256x512) where the
alpha cuts out the rectangle into a banana shaped image. The texture is
originally placed horizontally. It is rescaled/resized by a factor of 8.7594.
It is then slowly rotated counter clockwise. At about > 20 degrees, there are little
spots, maybe "twinkling pixels" would be a more accurate term. Or static on a TV.
Some of the spots (pixels) look like the blue is bleeding through and some of the
blue screen looks like it might have white pixels. At first there is one or two, and
then at lets say 30 degrees there might be as many as 15 of these spots. They
then decrease and go away as the angle goes to 90 degrees (vertical).

I don't think this is an example of tearing or antialiasing, but maybe I'm wrong.
Here's some of the things I've tried.

1) Originally was using mip maps. Tried just a simple texture. Same problem.

2) Tried all combinations of MAG_FILTER and MIN_FILTER. GL_NEAREST, GL_LINEAR,
and all the xxx_MIPMAP_xxx values.

4) glHint(all possibilities);

5) Tried not scaling the texture. ie scale factor = 1.0

6) Other stuff that I've tried over the year.

In desperation, I'm researching screen Anti-aliasing, fog, and lighting but
these seem kludgy at best.

Thought I had a break-thru with glLightModeli(___, GL_SEPARATE_SPECULAR_COLOR)
but nope.

Has anybody had any similiar experiences? Any suggestions or ideas?
Thanks.
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Luminary
Posts: 5,143
Joined: 2002.04
Post: #2
this thread has all your answers: http://www.idevgames.com/forum/showthread.php?t=7560
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Member
Posts: 321
Joined: 2004.10
Post: #3
Thanks for the link. I've never heard of premultiplied alpha channels and it does
look like a great technique and I'll put it in my toolbox. But the halo effect is
not really the problem I'm experiencing.

I've got "twinkling pixels" (never thought I'd use those words together) inside the texture. Kinda like static white noise on a TV only distributed lightly throughtout
the texture both on the opaque and transparent portions of the Alpha channel.
It's very subtle but viewable. Probably less than .025% of pixels are corrupted.

All the examples in the halo premultiplied examples were static. I'm getting this
problem when the texture is rotated starting at the 20 degree standard angle.

So I think I'm not out of the woods yet.
thanks.
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DoG
Moderator
Posts: 869
Joined: 2003.01
Post: #4
This practically cries for a screenshot.
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Member
Posts: 321
Joined: 2004.10
Post: #5
DoG Wrote:This practically cries for a screenshot.

I agree. Excuse me while I whip this.. I mean while I write a glReadBuffer()
routine so I can take a snapshot. Think I've got some routine I can resue.
Of course this will mean more problems that I'll have to post. Can you say
nested iDevGames threads Smile
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Sage
Posts: 1,234
Joined: 2002.10
Post: #6
If you run in a window just hit Cmd-Shift-3 to capture the screen.

(if you run fullscreen, Cmd-Shift-3 is broken as of 10.3.6)
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Member
Posts: 321
Joined: 2004.10
Post: #7
I've never included an image in a post, so this may not work. Currently,
I've got the image sitting on my desktop. I dragged it into this window,
and got a new path in ie address. I then clicked on the "Insert imgage" icon
and pasted the path. Sorry if this doesn't work. Here goes.


[img]file:///Macintosh%20HD/Desktop%20Folder/PixelProblem.jpg[/img]
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Sage
Posts: 1,199
Joined: 2004.10
Post: #8
You'll need to upload the image to a server -- iDisk, or whatever hosting space your ISP provides.
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Member
Posts: 321
Joined: 2004.10
Post: #9
I've finally got a very primative web site, with screen shots of the
problem. It's still with me. Here's the URL if anybody is curious.

http://home.earthlink.net/~heasers/id3.html


Any suggestions? Thanks.
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Luminary
Posts: 5,143
Joined: 2002.04
Post: #10
you're not using 16-bit textures or a 16-bit drawable are you?
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Member
Posts: 321
Joined: 2004.10
Post: #11
I'm using 32 bit RGBA. I am using the an alpha mask to draw the hull.
What commands would determing the "16 bit drawable" stuff.

I am using a 5 year old iMac G3 with god knows what video subsystem.
Rage 128, maybe?

The twinkling spots do disappear at certain zoom levels when I move
the camea in z axis.

Maybe its time to get that new G5 iMac. Waiting for tomorrow's announcements.

Smile
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Member
Posts: 168
Joined: 2004.10
Post: #12
As far as I know, iMac G3 doesn't have a video card at all. Or that is what I've been informed.
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Moderator
Posts: 508
Joined: 2002.09
Post: #13
iMac G3's have an Ati Rage Pro with 4 MB Vram, 2MB built in. On OS X that's not enough to run OpenGL apps. Trust me, I have an iMac blueberry and I couldn't play games on it.

OpenGL in software mode does work though, but slow.

"When you dream, there are no rules..."
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Sage
Posts: 1,234
Joined: 2002.10
Post: #14
It depends on the model of iMac; it ranges from a 2 meg RageII in the original Bondi blue to a 16 meg Rage128 Ultra in the last round of Indigo/Snow/Graphite.

To the original poster-- try your app on somebody else's hardware to see what happens.
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Member
Posts: 321
Joined: 2004.10
Post: #15
Would that be a Pentium or a PPC mac Smile
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