VERTEXDATA UV strange error - GameCreators Forum

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Quel

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Posted: 4th Mar 2011 07:37

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I have this short code, which creates a single plain, makes a mesh of it, so i can change the UV coordinates on the second blend layer for my fog of war function which is essential to make it working. (would be)

But there are some strange things, and what seems to be a bug.

First i don't get it why the vertex order is this messed up. It took hours doing nothing but guessing the vertices which triangle they belong to. (the one poly plain is made up of two triangles... just to let you know if haven't already)

The other thing is that although i recover the standard vertex positions using GET VERTEXDATA U() / V() commands, the second triangle gives messed up texture! WHY?! How can it be?

(also spent hours trying to figure out the right values manually, no luck... yeah i know UV coords. go from 0 to 1.0!)

Here is the code, please try out and give me some advice.

+ Code Snippet

make object plain 1,10,10
      make mesh from object 1,1
      
      lock vertexdata for mesh 1
     
	`First triangle
        set vertexdata uv 3,1, get vertexdata u(3),get vertexdata v(3)
        set vertexdata uv 4,1, get vertexdata u(4),get vertexdata v(4)
        set vertexdata uv 5,1, get vertexdata u(5),get vertexdata v(5)
        
	`Second triangle
        set vertexdata uv 1,1, get vertexdata u(1),get vertexdata v(1)
        set vertexdata uv 2,1, get vertexdata u(2),get vertexdata v(2)
        set vertexdata uv 6,1, get vertexdata u(6),get vertexdata v(6)
        
      unlock vertexdata
      
      delete object 1

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Jimpo

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Posted: 4th Mar 2011 16:37 Edited at: 4th Mar 2011 22:18

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First off, the first vertex in an object is referenced as index 0, not 1. Second, the vertex ordering is based off whether the plain uses the vertex buffer or the index buffer.

I don't know about the default plains, but I know the ones made using IanM's Matrix1 Utility plugin use the index buffer. This means there are only four vertices for the plain. The first triangle is made from vertices (0,1,2) and the second is made from (1,2,3). I'd imagine the default plains work similar.

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Van B

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Location: Sunnyvale

Posted: 4th Mar 2011 17:47

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This is a function I use to UV map a plain...

+ Code Snippet

function set_uvs(obj,tx,ty,tw,th)

   if object in screen(obj)=0 then exitfunction

`Set UV coordinates to suit sprite grid

   tx#=tx : ty#=ty : tw#=tw : th#=th
   xa#=tx#/tw#
   ya#=ty#/th#
   w#=1.0/tw#
   h#=1.0/th#
   xb#=xa#+w#
   yb#=ya#+h#

   lock vertexdata for limb obj,0,2

      for v=0 to 5

         if v=1 or v=3 or v=4 then uvx#=xb# else uvx#=xa#
         if v=0 or v=1 or v=3 then uvy#=ya# else uvy#=yb#

         set vertexdata uv v,uvx#,uvy#

      next v

   unlock vertexdata

endfunction

Used for tile sheets, so the function takes the object number, then the x and y tile coordinates, and the tile width and height. You could easily change it to take direct UV coordinates, maybe like this:

+ Code Snippet

function set_uvs(obj,xa#,ya#,xb#,yb#)

   if object in screen(obj)=0 then exitfunction

   lock vertexdata for limb obj,0,2

      for v=0 to 5

         if v=1 or v=3 or v=4 then uvx#=xb# else uvx#=xa#
         if v=0 or v=1 or v=3 then uvy#=ya# else uvy#=yb#

         set vertexdata uv v,uvx#,uvy#

      next v

   unlock vertexdata

endfunction

Hope this helps.

Health, Ammo, and bacon and eggs!

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Quel

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Posted: 5th Mar 2011 00:11

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Using this:

set vertexdata uv 1,0, get vertexdata u(1),get vertexdata v(1)
set vertexdata uv 2,0, get vertexdata u(2),get vertexdata v(2)
set vertexdata uv 3,0, get vertexdata u(3),get vertexdata v(3)
set vertexdata uv 4,0, get vertexdata u(4),get vertexdata v(4)
set vertexdata uv 5,0, get vertexdata u(5),get vertexdata v(5)
set vertexdata uv 6,0, get vertexdata u(6),get vertexdata v(6)

Shouldn't change ANYTHING, AT ALL.

No?

This is the basic problem, they get the same values they already have... and things just get messed up with the second triangle. No matter what method or structure, this seems to be an error in DBP.

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Green Gandalf

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Playing: Malevolence:Sword of Ahkranox, Skyrim, Civ6.

Posted: 5th Mar 2011 12:28

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If you use invalid vertex numbers then all sorts of strange things can happen. Just do what the other posters have suggested, i.e. use vertices 0 to 5 not 1 to 6.

However, as it happens your code doesn't seem to mess anything up here. That could be luck though.

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Quel

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Posted: 5th Mar 2011 12:42

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Well, would have been just fine to point it out this plain and simple.

Thank god you are here on this forum Gandalf.

This program has the poorest documentation ever, why don't they make a decent help file for it at last? When the user wants to actually DO SOMETHING outside of spheres shooting boxes in front of a scrolling background, you suddenly find yourself out of nowhere with your own luck. Especially the Memblock section. It is there, without practically any details.

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Jeff Miller

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Posted: 5th Mar 2011 12:59 Edited at: 5th Mar 2011 13:00

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Since you only seem to be interested in two triangles, presumably on one side of the plane, you really should look into making your own one-sided plane with IanM's plugin as mentioned by Jimpo. That keeps it clean, with 4 vertices, not six. Also, using that method you never have to scratch your head over the order in which the vertices are placed since you have created the order yourself. A final advantage, which I use a lot, is that if the plane is intended to hold a fixed startup location, you merely use the proper coordinates when you create the plane. You do not have to position it later.

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DarkBASIC Professional Discussion / VERTEXDATA UV strange error