GLSL shader weirdness

pbourke's picture

I have put a very simple composition here http://paulbourke.net/transient/Jafni/ The wird thing is that it works on many/most machines but occasionally it doesn't. It does not seem to be related to the graphics card. And today we had two iMacs, same OS version, same QC, same graphics card ... works on one and not the other. Ideas? ps: the bit that doesn't work is the middle top frame derived from the GLSL shader. pps: I've trimmed down the movies to short sections.

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.

cybero's picture
Re: GLSL shader weirdness

Thought it might be a bit wise issue , not so though; rendering your composition in either 32 bit or 64 bit QC results equally in a black empty RII output onto the middle sphere.

jrs's picture
Re: GLSL shader weirdness

Worked fine for me - 2010 mbp with an nvidia 330m

cybero's picture
Re: GLSL shader weirdness

Just goes to show .. mine was an nvidia 9400m , iMac 2009 OS X 10.9 [updated install, not clean install]

gtoledo3's picture
Re: GLSL shader weirdness

Hey there Paul!

This works ok over here... (nVidia 9600, 10.8).

I'd suggest you check the Gatekeeper settings on both machines - make sure the one that isn't rendering correctly has it turned off. Apparently now Gatekeeper can somehow manage to prevent code from executing even though the plugin bundle has loaded and is able to be viewed in the editor. Since the part that isn't evaluating is inside the GL Ortho, it seems like this is a possible cause.

Maybe also scrutinize the vertex shader - I'm unsure that the if case really needs to be there, and if it does, you probably shouldn't be declaring phi first (though it shouldn't really make a difference). This makes it so that in the case that if rxy was to =0, you'd have an unused variable... which seems like it shouldn't be a problem, but I've seen things like this cause problems in edge cases.

cybero's picture
Re: GLSL shader weirdness

Interesting point about Gatekeeper.

Not relevant in this case though.

Gatekeeper off here, Paul's composition not rendering the centre sphere; problem seems to be quite specific to either OS and / or machine build.

destroythings's picture
Re: GLSL shader weirdness

Working fine here mavericks and a GT 650M

gtoledo3's picture
Re: GLSL shader weirdness

cybero wrote:
Interesting point about Gatekeeper.

Not relevant in this case though.

Gatekeeper off here, Paul's composition not rendering the centre sphere; problem seems to be quite specific to either OS and / or machine build.

Hey Cybero, does any image come out of the output port of the render in image, or is it dead there? Does the chain stop evaluating somewhere or does it just turn black somewhere along the way?

pbourke's picture
Re: GLSL shader weirdness

On the machines I find where it doesn't work, I get what looks like a blurred + pixellated image. See attached.

PreviewAttachmentSize
Screen Shot 2013-11-03 at 7.14.10 pm (2).png
Screen Shot 2013-11-03 at 7.14.10 pm (2).png1.09 MB