I suppose I have no choise.
Thanks for your quickly answer.

Hi:

I´m working with heavy lists. And I want to change the transparency of all elements of the list. Now I´m deleting and creating the list again, what is very inefficient and it works very slow. The question is if it is possible to apply a global transparency to one list just before I draw it  ( glCallList ).

Regards.

Your are right. It is a problem of the normal. If I change the points to calculate the normal, sometimes it draws correctly, but others it doesn´t, but I don´t know how to know if the normal is correctly calculated. I use always the same code to calculate it. Some idea?

Hi again.
Thanks for the answer.

Now I have all my polygons directed to the same side, and the most of the polygons show correctly. But I continue with a problem. Some of the polygons appear black, they doesn´t apply the color that I have put to gl. I have made some tests and it seems to be related with concave and convex polygons, because when I delete some point it works. I delete the points which go toward the inside of the polygon.
I´m going to try to show an example of two polygons (with extrude) that execute the same code, the only difference is one point. Do you have some idea how to solve it??
Regards

I´m trying to get access to the process of creating shapes, perhaps I can transform some code. But I can´t solve one problem. How to know when a polygon is given in counter-clockwise order, or if the ordering is clockwise.
Thanks for your answers

Thanks for the answer lhkbob.
I have no control to create the shapes, so I can´t choose the order of vertices. I have tried with glLightModeli(GL_LIGHT_MODEL_TWO_SIDE, GL_TRUE), but it change the face which is lighted, but it doesn´t light the two faces of shapes.

Hi.
I have a problem with lights, and I can´t solve it.
I´m drawing several shapes which are composed by polygons. I apply the same colors and lights to all shapes. All polygons have one face lighted and the other shaded. The problem is that in some shapes the faces lighted are just the opposite that in the others, and this causes an annoyed scene.
I have made some tests, and I can change the face lighted inserting the points just in the opposite order, but I can´t control this with a lot of shapes.

Is there any way to light the two faces of the polygons (   I have tried with glMaterialfv(GL.GL_FRONT_AND_BACK,   doesn´t work to me  ), or how can I get to light always the face in the same orientation??

Thanks.

Hi again.

I have another question. I´m drawing a shape3D, but I want to draw it in a position of the canvas which I have the position (in pixels). The problem is I don´t know how to do the matching between the pixels in the canvas and the space coordinates.

Some idea??

I´m going to take a look what you say.
Thanks to both for the answers 

Thanks again. I´m going to try it .

Thanks a lot for the answer. I don´t have clear one thing. In this example the object BufferedImage out what you return has all image or only the part that you clipped. If it is only the part that you clipped it is what I need.

Thanks again.

Hi everyone:

I have an image file and the coordinates of the triangles that the GL object uses to cut the image and draw the differents parts. I use the method "glTexCoordPointer" of the GL object to assign the Texture coordinates.
Is there any way to get a different BufferedImage from each triangle of the image that the GL object creates?

Thanks.

Hi everyone:

I have a difficult problem to solve.
I have a Shape3D object (with his TextureImage2D and his Geometry). The TextureImage2D is loaded from an image file. I need to get a BufferedImage to each part of the Shape3D object or to each Triangle of the shape. I only can get the BufferedImage from all the image file.
May be some option to get differents images from the original image file using the texture coordinates?

Thanks