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Alpha map shadow problem
Hi all,
I have made an intro animation of a card opening. The card has a die-cut pattern which I have used an alpha map to cut out the card. It works fine, except that the shadow that falls on the card is not based on the cut-out alpha, but the polygon plane of the card, which is a rectangle.
Ho do I get the cut-out pattern to cast the correct shadow instead of the bounding rectangle frame.
The main spotlight source shadow is cast using area shadow settings and I have checked to make sure the transparency in the render setting is turned on.
What could have caused this?
Ken
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11 Replies
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probably don’t have Transparency checked in the Shadow tab of the lights attributes
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Hi Brian,
I have that turned on, but does not seems to work.
I was doodling with the material editor and tried making a new material with only the alpha map turned on and add it to the other textures to the card. It seems to work.
Don’t know how I do it, it seems that it only work with the alpha map on a new material and stacked together with other material, instead of just using one material with the colour and alpha map turned on.
Guess I have to dig deeper into how material works in the oject menu.
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Hmmm… works with color and alpha here, can you post an example scene?
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Sure, but how do I post an image on this forum, can you give me your email so I can send the examples to you?
Thanks
Ken
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Hi Brian,
Yes, your alpha works, but it is only for simple one texture object, my is more complex with several material stack on top of the other. Still don’t know how the stacking works, did it by trial & error.
I have put up a link to an example file on my .Mac page, please ignore those texture that prompts you, the textures that correctly represents the image should already load in the first frame. Included a right & wrong image for reference
If this link don’t work, try this https://homepage.mac.com/kismef/.Public/shadow_cut.zip
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I’d send you an example but I don’t have 10 yet. Card Top is not a single poly it’s a very flat box. Normals mostly pointing inward. Card Mat was set to Back for the Side (in the texture tag) so it’s alpha was only showing the flat grey of the front side of the poly that is the bottom of the box that ‘card top’ really is – it was not a failure of alpha, just not enough alpha to get through both sides of all polys in the box.
You can do it with a single texture. Highlights was doing nothing except giving you an alpha (because it was set to Both for Sides) so toss it, put the bump map in the bump channel of Card Mat, toss the ‘border bump’ material and set Side in Card Mat’s texture tag to both.Not needed here but for more info on stacking materials and mixing textures search Help for Texture Tag choose Tag Properties (Texture Tag) and scroll to close to the bottom (Texture Layering and Mix Textures). If you’ve read that already, never mind 🙂
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Hi Brian,
Sorry for the late response, have been doing other project and have put this project on the hold for a while.
Thanks for the info, I had forgotten that my card top was a flat cube, no wonder the alpha map do not work after choosing several projection.
However, now I have another problem, the bump map that I have applied seems to stutter around as the card moves, what could have caused this?
Sorry to trouble you again
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“Stutter around”? Actual movement or just the usual shimmery antialiasing thing?
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Hi Brian,
It is not shimmering, it is flickering on the same spot, sort of like emboss and deboss at the same time.
I have zipped a quicktime mov file and a screen grab for the setup to help you understand better. I have also tried to put the bump together in one texture, the same problem appears. I am using UVW Mapping on both side.
What could caused this?
Here is the link
https://homepage.mac.com/kismef/.Public/bump_problem.zip
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