Getting the face normal in the frag shader?

Troubleshooting graphics
1

sigh Here we go again…

Short version:
How does one get the normal vector of the triangle being rendered in the frag shader of a multi-polygon mesh?

List of stuff I’ve tried (in the vert shader, vNormal is a varying passed to the frag shader):

  • vNormal = normalize(g_NormalMatrix * inNormal); [as seen in Lighting.vert]
  • vNormal = normalize((g_WorldMatrix * vec4(0.0, 0.0, 1.0, 0.0)).xyz); [works for individual quads]

Long version

So what I have is a bunch of quads that are randomly placed in space with the same material.

image_20160404_162700.png670×540 75.8 KB

Their parent node is then passed to the GeometryBatchFactory.optimize() which reduces it to a geometry that I reattach to another node to get rid of the leftover junk geometries.

Now the mesh itself renders correctly (after I reapply some parameters to it). However the shader that used to work for individual quads now doesn’t do it’s job right anymore.

What it’s supposed to do is to scale the transparency of the quads depending on the dot product with the camera view vector like so:

color.a = abs(dot(viewDir, vNormal)) - 0.2;

And the viewDir and vNormal are obtained in the vert shader as you can see here:

vec3 worldPosition = (g_WorldMatrix * vec4(inPosition, 1.0)).xyz;

viewDist = length(g_CameraPosition - worldPosition);
viewDir = normalize(g_CameraPosition - worldPosition).xyz;
vNormal = normalize((g_WorldMatrix * vec4(0.0, 0.0, 1.0, 0.0)).xyz);

Again, this worked for separate non-batched quads.

Any ideas?

P. S.

I tried the solution from here and it doesn’t seem to be working in any meaningful way.

2

So you want the normal in world space?
inNormal : is the normal in model space
normalize((g_WorldMatrix*vec4(inNormal,0.0)).xyz) : is the normal in world space

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3

That works! :smiley: Well this was straightforward.

Dat feel when you reduce 500 draw calls to 1.

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4

As my thanks, I can show you my next optimization step. Goofy testing of the nebula cloud atlas. Also since the colors are now randomised adjusted in the shader they can change color slightly over time too.

image_20160809_173401.png1920×1080 1.8 MB

Tex :stuck_out_tongue: :

0.png760×760 84.4 KB

In case it’s useful for anyone, it’s done via:

Quad[] plates = new Quad[4];

Quad side = new Quad(size,size);
side.setBuffer(Type.TexCoord, 2, new float[]{0,0.5f,     0.5f,0.5f,     0.5f,0,    0,0});
plates[0]= side;
  	  	
side = new Quad(size,size);
side.setBuffer(Type.TexCoord, 2, new float[]{0.5f,1,     1,1,     1,0.5f,    0.5f,0.5f});
plates[1]= side;
  	  	
side = new Quad(size,size);
side.setBuffer(Type.TexCoord, 2, new float[]{0.5f,0.5f,     1,0.5f,     1,0,    0.5f,0});
plates[2]= side;
  	  	
side = new Quad(size,size);
side.setBuffer(Type.TexCoord, 2, new float[]{0,1,     0.5f,1,     0.5f,0.5f,    0,0.5f});
plates[3]= side;

And then a random quad selected when making the geometry.

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