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jPCT-AE - a 3d engine for Android => Support => Topic started by: Hellfire on November 25, 2022, 03:45:26 pm

Title: How does JPCT-AE Vertex works on Object3D.addTriangle(...)?
Post by: Hellfire on November 25, 2022, 03:45:26 pm

Hello friends. How does JPCT-AE Vertex works on Object3D.addTriangle(...)?

Code: [Select]

public static Object3D createCube(float scale) {
 Object3D o = new Object3D(12);
 float size = scale / 2;

// FRONT
 o.addTriangle(new SimpleVector(-size, size, size), new SimpleVector(-size, -size, size), new SimpleVector(size, size, size));
 o.addTriangle(new SimpleVector(size, size, size), new SimpleVector(size, -size, size), new SimpleVector(-size, -size, size));

// BACK
 o.addTriangle(new SimpleVector(-size, size, -size), new SimpleVector(-size, -size, -size), new SimpleVector(size, size, -size));
 o.addTriangle(new SimpleVector(size, size, -size), new SimpleVector(size, -size, -size), new SimpleVector(-size, -size, -size));

// LEFT
 o.addTriangle(new SimpleVector(-size, size, size), new SimpleVector(-size, -size, size), new SimpleVector(-size, size, -size));
 o.addTriangle(new SimpleVector(-size, size, -size), new SimpleVector(-size, -size, -size), new SimpleVector(-size, -size, size));
 
// RIGHT
 o.addTriangle(new SimpleVector(size, size, size), new SimpleVector(size, -size, size), new SimpleVector(size, size, -size));
 o.addTriangle(new SimpleVector(size, size, -size), new SimpleVector(size, -size, -size), new SimpleVector(size, -size, size));

// UPPER
 o.addTriangle(new SimpleVector(size, size, size), new SimpleVector(-size, size, size), new SimpleVector(size, size, -size));
 o.addTriangle(new SimpleVector(size, size, -size), new SimpleVector(-size, size, -size), new SimpleVector(-size, size, size));

// LOWER
 o.addTriangle(new SimpleVector(size, -size, size), new SimpleVector(-size, -size, size), new SimpleVector(size, -size, -size));
 o.addTriangle(new SimpleVector(size, -size, -size), new SimpleVector(-size, -size, -size), new SimpleVector(-size, -size, size));
 return o;
}
Result:

Title: Re: How does JPCT-AE Vertex works on Object3D.addTriangle(...)?
Post by: EgonOlsen on November 26, 2022, 09:31:27 pm

Order matters here. jPCT culls away back faces (unless you disable this with setCullling(), but the lighting will be wrong in this case). What is a back face and what isn't is defined by the order of the vertices in a triangle. In this case, reverse the order of the vertices for the faces that aren't visible and they should show up.