Hi, I want to apply colors (or textures) with alpha values to obj. models and then turn them around, but I am having problems if I rotate the objects. this actually causes problems with standard geos, too... I searched the archives for that problem but I found no real answer. maybe because there is none? what is necessary to get transparency working from all different viewpoints? I tried to play around with GEMglDepthFunc and other stuff, but not with the correct result. (correct maybe, but not what I wanted.) any help? thanks, marius.
On Fri, 2008-04-04 at 22:42 -0400, marius schebella wrote:
Hi, I want to apply colors (or textures) with alpha values to obj. models and then turn them around, but I am having problems if I rotate the objects. this actually causes problems with standard geos, too... I searched the archives for that problem but I found no real answer. maybe because there is none?
iirc, it was discussed before (otherwise i wouldn't be able to write you a reply).
from what i understand, alpha rendering depends on rendering order. first, the textures most behind need to be rendered in order to get transparency for textures more in front.
what is necessary to get transparency working from all different viewpoints?
i don't know if there is a general solution. would be interested as well.
I tried to play around with GEMglDepthFunc and other stuff, but not with the correct result. (correct maybe, but not what I wanted.) any help? thanks,
i don't know about [GEMglDepthFunc], but a not very realistic approach could be to split a model into its planes and change the rendering order of the planes dynamically, so that most-behind planes are rendered first and most-in-front planes rendered last. calculating the correct rendering order needs a lot of math and i don't quit know how to do it.
roman
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hi H, list in my experience the proper order of objects is
gemhead I pix_image I alpha 1 I colorRGB I pix_texture I model
you can then play with the last inlet of [colorRGB] to fade in/out geos/models. Correct me if im wrong - [alpha 1] should be before [pix_texture] in the chain to be rendered correctly. here are two of my patches using a lot of transparency tricks, hope this helps
www.njeremic.ecobytes.net/files/vj-live1.zip www.njeremic.ecobytes.net/files/baum_pd_patch.zip
greetings n.
Roman Haefeli wrote:
On Fri, 2008-04-04 at 22:42 -0400, marius schebella wrote:
Hi, I want to apply colors (or textures) with alpha values to obj. models and then turn them around, but I am having problems if I rotate the objects. this actually causes problems with standard geos, too... I searched the archives for that problem but I found no real answer. maybe because there is none?
iirc, it was discussed before (otherwise i wouldn't be able to write you a reply).
from what i understand, alpha rendering depends on rendering order. first, the textures most behind need to be rendered in order to get transparency for textures more in front.
what is necessary to get transparency working from all different viewpoints?
i don't know if there is a general solution. would be interested as well.
I tried to play around with GEMglDepthFunc and other stuff, but not with the correct result. (correct maybe, but not what I wanted.) any help? thanks,
i don't know about [GEMglDepthFunc], but a not very realistic approach could be to split a model into its planes and change the rendering order of the planes dynamically, so that most-behind planes are rendered first and most-in-front planes rendered last. calculating the correct rendering order needs a lot of math and i don't quit know how to do it.
roman
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On Sat, 2008-04-05 at 12:47 +0200, niko wrote:
hi H, list in my experience the proper order of objects is
as far as i understand marius, he doesn't have troubles with implementing transparency in general. the problem is rather, that if you have a cube for example and you apply a texture with transparency to it, it works well, but if you rotate the cube around 180°, transparency doesn't work anymore. or more correct: transparent parts of the plane in front don't show parts of the plane behind, but of the background (or whatever was rendered first _and_ is behind the front plane).
sorry, if i repeat myself, but i have troubles finding a better explanation.
roman
gemhead I pix_image I alpha 1 I colorRGB I pix_texture I model
you can then play with the last inlet of [colorRGB] to fade in/out geos/models. Correct me if im wrong - [alpha 1] should be before [pix_texture] in the chain to be rendered correctly. here are two of my patches using a lot of transparency tricks, hope this helps
www.njeremic.ecobytes.net/files/vj-live1.zip www.njeremic.ecobytes.net/files/baum_pd_patch.zip
greetings n.
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Hello Roman, Marius, Niko and list ! Here a small patch for this problem. Sorry, i have not enough time for a patch with dynamic creation of geos. ++
Jack
Le 5 avr. 08 à 13:06, Roman Haefeli a écrit :
On Sat, 2008-04-05 at 12:47 +0200, niko wrote:
hi H, list in my experience the proper order of objects is
as far as i understand marius, he doesn't have troubles with implementing transparency in general. the problem is rather, that
if you have a cube for example and you apply a texture with transparency
to it, it works well, but if you rotate the cube around 180°, transparency doesn't work anymore. or more correct: transparent parts of the
plane in front don't show parts of the plane behind, but of the background (or whatever was rendered first _and_ is behind the front plane).sorry, if i repeat myself, but i have troubles finding a better explanation.
roman
gemhead I pix_image I alpha 1 I colorRGB I pix_texture I model
you can then play with the last inlet of [colorRGB] to fade in/out geos/models. Correct me if im wrong - [alpha 1] should be before [pix_texture] in the chain to be rendered correctly. here are two of my patches using a lot of transparency tricks,
hope this helpswww.njeremic.ecobytes.net/files/vj-live1.zip www.njeremic.ecobytes.net/files/baum_pd_patch.zip
greetings n.
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In fact, it's not very good, because the position depends on the
center of the geos.
But it can be useful in certain case.
++
Jack
Le 5 avr. 08 à 15:23, Jack a écrit :
Hello Roman, Marius, Niko and list ! Here a small patch for this problem. Sorry, i have not enough time for a patch with dynamic creation of
geos. ++Jack
<testorder1.pd> Le 5 avr. 08 à 13:06, Roman Haefeli a écrit :
On Sat, 2008-04-05 at 12:47 +0200, niko wrote:
hi H, list in my experience the proper order of objects is
as far as i understand marius, he doesn't have troubles with implementing transparency in general. the problem is rather, that
if you have a cube for example and you apply a texture with transparency
to it, it works well, but if you rotate the cube around 180°, transparency doesn't work anymore. or more correct: transparent parts of the
plane in front don't show parts of the plane behind, but of the background (or whatever was rendered first _and_ is behind the front plane).sorry, if i repeat myself, but i have troubles finding a better explanation.
roman
gemhead I pix_image I alpha 1 I colorRGB I pix_texture I model
you can then play with the last inlet of [colorRGB] to fade in/out geos/models. Correct me if im wrong - [alpha 1] should be before [pix_texture] in the chain to be rendered correctly. here are two of my patches using a lot of transparency tricks,
hope this helpswww.njeremic.ecobytes.net/files/vj-live1.zip www.njeremic.ecobytes.net/files/baum_pd_patch.zip
greetings n.
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hmm, something in your patch is crashing my pd, the transparency is also not working correct, in some situations the render order is still wrong (when circles are rotated and the scene as a whole) and I also get flicker when the render order changes. plus, this still does not help me with wavefront models... but in theory something like changing the render order is the solution. marius.
Jack wrote:
Hello Roman, Marius, Niko and list ! Here a small patch for this problem. Sorry, i have not enough time for a patch with dynamic creation of geos. ++
Jack
Le 5 avr. 08 à 13:06, Roman Haefeli a écrit :
On Sat, 2008-04-05 at 12:47 +0200, niko wrote:
hi H, list in my experience the proper order of objects is
as far as i understand marius, he doesn't have troubles with implementing transparency in general. the problem is rather, that if you have a cube for example and you apply a texture with transparency to it, it works well, but if you rotate the cube around 180ð, transparency doesn't work anymore. or more correct: transparent parts of the plane in front don't show parts of the plane behind, but of the background (or whatever was rendered first _and_ is behind the front plane).
sorry, if i repeat myself, but i have troubles finding a better explanation.
roman
gemhead I pix_image I alpha 1 I colorRGB I pix_texture I model
you can then play with the last inlet of [colorRGB] to fade in/out geos/models. Correct me if im wrong - [alpha 1] should be before [pix_texture] in the chain to be rendered correctly. here are two of my patches using a lot of transparency tricks, hope this helps
www.njeremic.ecobytes.net/files/vj-live1.zip www.njeremic.ecobytes.net/files/baum_pd_patch.zip
greetings n.
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On Sat, 2008-04-05 at 12:47 +0200, niko wrote:
www.njeremic.ecobytes.net/files/baum_pd_patch.zip
hi again. i stumbled across a rendering of this one somewhere, can't recall where exactly. however, i just wanted to say, that i really enjoyed it.
roman
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thanx i already posted it here before there is a videoof it http://www.njeremic.ecobytes.net/njeremic/videos/baum_net.mov greets. n.
p.s. sorry for not understanding the original post question i also needed a long time to understand transparency in gem/openGL
Roman Haefeli wrote:
On Sat, 2008-04-05 at 12:47 +0200, niko wrote:
www.njeremic.ecobytes.net/files/baum_pd_patch.zip
hi again. i stumbled across a rendering of this one somewhere, can't recall where exactly. however, i just wanted to say, that i really enjoyed it.
roman
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hello,
for what i know, this is a openGL limitation, with no generic hardware solution.
cyrille
marius schebella a écrit :
Hi, I want to apply colors (or textures) with alpha values to obj. models and then turn them around, but I am having problems if I rotate the objects. this actually causes problems with standard geos, too... I searched the archives for that problem but I found no real answer. maybe because there is none? what is necessary to get transparency working from all different viewpoints? I tried to play around with GEMglDepthFunc and other stuff, but not with the correct result. (correct maybe, but not what I wanted.) any help? thanks, marius.
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but I have the impression that some program manage to solve that problem. I am not sure how, but if there is a solution, then it should also be possible to use it in gem. often I am not sure if people are talking about single objects or secenes. but afaik it has something to do with a z-buffer, like it would be possible to render the obj coordinates from the camera viewpoint into a special alpha channel/buffer and then use that information to define the renderorder for the texture. but not sure at all, if this is my fantasy or if that is really how it works. I know that shadows also se weird buffers and viewpoint manipulations to work. thanks roman, cyrille for your answers, I am aware of the discussions in the archive, maybe some more talk brings us further... marius.
cyrille henry wrote:
hello,
for what i know, this is a openGL limitation, with no generic hardware solution.
cyrille
marius schebella a écrit :
Hi, I want to apply colors (or textures) with alpha values to obj. models and then turn them around, but I am having problems if I rotate the objects. this actually causes problems with standard geos, too... I searched the archives for that problem but I found no real answer. maybe because there is none? what is necessary to get transparency working from all different viewpoints? I tried to play around with GEMglDepthFunc and other stuff, but not with the correct result. (correct maybe, but not what I wanted.) any help? thanks, marius.
PD-list@iem.at mailing list UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list
You want to sort by Z which requires special depth sorting code in the external. The model object uses a display list so you would have to stop using that and move to vertex arrays for decent performance.
On Sat, Apr 5, 2008 at 7:21 AM, marius schebella marius.schebella@gmail.com wrote:
but I have the impression that some program manage to solve that problem. I am not sure how, but if there is a solution, then it should also be possible to use it in gem. often I am not sure if people are talking about single objects or secenes. but afaik it has something to do with a z-buffer, like it would be possible to render the obj coordinates from the camera viewpoint into a special alpha channel/buffer and then use that information to define the renderorder for the texture. but not sure at all, if this is my fantasy or if that is really how it works. I know that shadows also se weird buffers and viewpoint manipulations to work. thanks roman, cyrille for your answers, I am aware of the discussions in the archive, maybe some more talk brings us further... marius.
cyrille henry wrote:
hello,
for what i know, this is a openGL limitation, with no generic hardware solution.
cyrille
marius schebella a écrit :
Hi, I want to apply colors (or textures) with alpha values to obj. models and then turn them around, but I am having problems if I rotate the objects. this actually causes problems with standard geos, too... I searched the archives for that problem but I found no real answer. maybe because there is none? what is necessary to get transparency working from all different viewpoints? I tried to play around with GEMglDepthFunc and other stuff, but not with the correct result. (correct maybe, but not what I wanted.) any help? thanks, marius.
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I have done this very fast, so it's not really good (slow)… Yep, i know it's not good, but it could be interesting. If someone rewrite, it would be nice ! (i have not time to work on it)
Frank, do you have somewhere an abstraction to order list (asc and
desc). Maybe you could add it in list-abs library, or i miss
something (of course, i think my abstraction need to be rewrite) ?
++
Jack

Le 5 avr. 08 à 17:54, chris clepper a écrit :
You want to sort by Z which requires special depth sorting code in
the external. The model object uses a display list so you would
have to stop using that and move to vertex arrays for decent
performance.On Sat, Apr 5, 2008 at 7:21 AM, marius schebella
marius.schebella@gmail.com wrote: but I have the impression that some program manage to solve that problem. I am not sure how, but if there is a solution, then it should also be possible to use it in gem. often I am not sure if people are talking about single objects or secenes. but afaik it has something to do with a z-buffer, like it
would be possible to render the obj coordinates from the camera viewpoint
into a special alpha channel/buffer and then use that information to define the renderorder for the texture. but not sure at all, if this is my fantasy or if that is really how it works. I know that shadows also se weird buffers and viewpoint manipulations to work. thanks roman, cyrille for your answers, I am aware of the
discussions in the archive, maybe some more talk brings us further... marius.cyrille henry wrote:
hello,
for what i know, this is a openGL limitation, with no generic
hardware
solution.
cyrille
marius schebella a écrit :
Hi, I want to apply colors (or textures) with alpha values to obj.
models
and then turn them around, but I am having problems if I rotate the objects. this actually causes problems with standard geos, too... I searched the archives for that problem but I found no real
answer.
maybe because there is none? what is necessary to get transparency working from all different viewpoints? I tried to play around with GEMglDepthFunc and other stuff, but not with the correct result. (correct maybe, but not
what I
wanted.) any help? thanks, marius.
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chris clepper -
cyrille henry -
Jack -
marius schebella -
niko -
Roman Haefeli