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# Weird tiled effect with calculating Normals, TRIANGLE_STRIPS

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#### Ziath

• 5
##### Weird tiled effect with calculating Normals, TRIANGLE_STRIPS
« on: June 02, 2013, 03:37:52 »
I've made a height map program and i'm trying to calculate normals for each vertex. I've tried searching for a solution all morning but i can not figure out the error in my code. I am getting a weird tiled effect as you can see in the picture below.. I'm using triangle strips to render a 400 by 400 vertice plane. I have set all y values to 0 for this post. If anyone could help, and point out whats wrong, that would be awesome

http://imgur.com/ICeksXX

Code: [Select]
`public void calculateNormals() { for (int n = 0; n < 400*200; n++) { float x1 = vBuffer.get(n + 0); float y1 = vBuffer.get(n + 1); float z1 = vBuffer.get(n + 2); float x2 = vBuffer.get(n + 3); float y2 = vBuffer.get(n + 4); float z2 = vBuffer.get(n + 5); float x3 = vBuffer.get(n + 6); float y3 = vBuffer.get(n + 7); float z3 = vBuffer.get(n + 8); float Ux = (x2 - x1); float Uy = (y2 - y1); float Uz = (z2 - z1); float Vx = (x3 - x1); float Vy = (y3 - y1); float Vz = (z3 - z1); float Nx = Uy*Vz - Uz*Vy; float Ny = Uz*Vx - Ux*Vz; float Nz = Ux*Vy - Uy*Vx; float normLength = (float)Math.sqrt(Math.pow(Nx,2) + Math.pow(Ny,2) + Math.pow(Nz,2)); if(normLength == 0){ Nx = 0; Ny = 0; Nz = 0; }else{ Nx /= normLength;     Ny /= normLength;     Nz /= normLength; } if ((n %2)==0){ nBuffer.put(Nx).put(Ny).put(Nz); } else{ nBuffer.put(-Nx).put(-Ny).put(-Nz); } } this.nBuffer.flip(); } `

#### Fool Running

• 828
##### Re: Weird tiled effect with calculating Normals, TRIANGLE_STRIPS
« Reply #1 on: June 03, 2013, 17:22:19 »
the n++ in your loop looks suspicious. It looks like it should be += 3.

P.S. Math.pow(Nx,2) is a lot slower then Nx * Nx.
Programmers will, one day, rule the world... and the world won't notice until its too late.Just testing the marquee option

#### quew8

• 569
• Because Square Eyes Look More Real
##### Re: Weird tiled effect with calculating Normals, TRIANGLE_STRIPS
« Reply #2 on: June 03, 2013, 21:16:05 »
For the record it is a pretty cool effect. I would just keep it as bugs influencing design style. If you want rid of it, I second @Fool Running.

For the record I would also recommend using LWJGL's vector classes or writing your own, it makes higher level maths so much easier. (I know this isn't really high level but...)