Frederic Bouvier wrote:
Quoting Robicd :
I've made some other tryout and I've come to a functioning technique
that I don't like very much though.
The only way I've found, by now, consists in making use of two planes,
the one on top of the other.
I build first an underlaying yellow emitting square plane, then I modell
another plane obove the first, this second plane having a black letter
on transparent background file texture.
This way I get a correct yellow emission in the background and a clear
black letter above it (the alpha channel of the c letter file makes me
see through it).
But I would like not to use two distinct planes for such a simple 3d
object. I'd like to make it even simpler then that; I wonder if there's
a way to let the .ac file describe this modelling scenario too.
A texture, in the way plib use them, can only bring diffuse color and
transparency. And plib uses modulation of colors between the texture and the
material color. That means that each color components from the texture are
multiplied with the corresponding color of the material. The consequence of
this is that a white material is neutral on the color texture, and a black
material zero the texture color. And the inverse is true too and also apply to
the alpha channel.
The way to solve your problem is :
1. draw a texture ( in Gimp ) with a black letter on a yellow background and no
alpha channel ( no transparency ).
2. create a white material in AC3D ( or in Blender ) with an emissive white
component.
3. draw a square in AC3D and affect it the white emissive material.
4. map the yellow/black texture on the emissive white square.
Voila
-Fred
Thank you Fred,
that was a very simple and complete answer to my question. Explaining
the way Plib builds the resulting colors from texture and material color
informations has been the final solution to my problem :-)
Now I have modelled a simple L-858Y.ac prototype of a Runway Exit Sign,
I'd like someone chek out for comments. I used the FAA A/C 150/5345-44G
and 150/5340-18D in order to get some realistic measures. Melchior was
very helpfull having released a very good runway.ttf font file, he used
a few pictures out of the above mentioned A/C for correct outlines and
proportion.
The .ac file provides geometry for one and two sides signs, it can be
customized with the L-858Y.xml file.
The sign faces emit a yellow background light; that can be changed to
red or white wth the .xml material animation.
The sign faces being displaced can be changed with sign-face and
sign-face2 objects' texture material animation.
The frame color can be changed with the diffuse material animation.
The LOD sets to 2000m the maximum distance you can see the sign faces
and to 300m for the remaining part of the model. I think that's a good
compromise.
This 3d object can be used as a base for creating a whole set of runway
signs by changing dimensions of the base object and providing a complete
set of textures.
You get the zip file with the prototype and a few screenshots at
http://www.geocities.com/robitabu/animation/signs/
cheers,
Roberto
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