问题描述
该项目完全是用Java从头编写的。自Covid成立以来，我一直很无聊，所以我想要可以占用我时间的东西，并教给我一些很棒的东西。我已经在这个问题上停留了大约一个星期。当我尝试使用近平面剪裁方法时，它会将新的顶点倾斜到屏幕的另一侧，但有时效果很好。
所以我想也许是因为有时它会起作用，所以我只是没有在管道中的正确时间进行剪辑？
我从面部剔除和照明开始，
然后我将“摄影机视图”变换应用于顶点，
然后我在近平面上修剪
最后，我应用投影矩阵并裁剪掉屏幕上所有剩余的三角形
代码：
这将计算交点。抱歉，如果我很杂乱或者很长一段时间，我没有编码方面的经验，我的专业是物理学，而不是CS。
public Vertex vectorIntersectPlane(Vector3d planePos,Vector3d planenorm,Vector3d linestart,Vector3d lineEnd){
float planeDot = planenorm.dotProduct(planePos);
float startDot = linestart.dotProduct(planenorm);
float endDot = lineEnd.dotProduct(planenorm);
float midPoint = (planeDot - startDot) / (endDot - startDot);
Vector3d linestartEnd = lineEnd.sub(linestart);
Vector3d linetoIntersect = linestartEnd.scale(midPoint);
return new Vertex(linestart.add(linetoIntersect));
}
public float distanceFromPlane(Vector3d planePos,Vector3d vert){
float x = planenorm.getX() * vert.getX();
float y = planenorm.getY() * vert.getY();
float z = planenorm.getZ() * vert.getZ();
return (x + y + z - (planenorm.dotProduct(planePos)));
}
//When a triangle gets clipped it has 4 possible outcomes
// 1 it doesn't actually need clipping and gets returned
// 2 it gets clipped into 1 new triangle,for testing these are red
// 3 it gets clipped into 2 new triangles,for testing 1 is green,and 1 is blue
// 4 it is outside the view planes and shouldn't be rendered
public void clipTriangles(){
Vector3d planePos = new Vector3d(0,ProjectionMatrix.fNear,1f);
Vector3d planenorm = Z_AXIS.clone();
final int length = triangles.size();
for(int i = 0; i < length; i++) {
Triangle t = triangles.get(i);
if(!t.isDraw())
continue;
Vector3d[] insidePoint = new Vector3d[3];
int insidePointCount = 0;
Vector3d[] outsidePoint = new Vector3d[3];
int outsidePointCount = 0;
float d0 = distanceFromPlane(planePos,planenorm,t.getVerticesvectors()[0]);
float d1 = distanceFromPlane(planePos,t.getVerticesvectors()[1]);
float d2 = distanceFromPlane(planePos,t.getVerticesvectors()[2]);
//Storing distances from plane and counting inside outside points
{
if (d0 >= 0){
insidePoint[insidePointCount] = t.getVerticesvectors()[0];
insidePointCount++;
}else{
outsidePoint[outsidePointCount] = t.getVerticesvectors()[0];
outsidePointCount++;
}
if (d1 >= 0){
insidePoint[insidePointCount] = t.getVerticesvectors()[1];
insidePointCount++;
}else{
outsidePoint[outsidePointCount] = t.getVerticesvectors()[1];
outsidePointCount++;
}
if (d2 >= 0){
insidePoint[insidePointCount] = t.getVerticesvectors()[2];
insidePointCount++;
}else{
outsidePoint[outsidePointCount] = t.getVerticesvectors()[2];
}
}
//Triangle has 1 point still inside view,remove original triangle add new clipped triangle
if (insidePointCount == 1) {
t.dontDraw();
Vertex newVert1 = vectorIntersectPlane(planePos,insidePoint[0],outsidePoint[0]);
Vertex newVert2 = vectorIntersectPlane(planePos,outsidePoint[1]);
vertices.add(newVert1);
vertices.add(newVert2);
//Triangles are stored with vertex references instead of the actual vertex object.
Triangle temp = new Triangle(t.getVertKeys()[0],vertices.size() - 2,vertices.size() - 1,vertices);
temp.setColor(1,t.getBrightness(),t.getAlpha());
triangles.add(temp);
continue;
}
//Triangle has two points inside remove original add two new clipped triangles
if (insidePointCount == 2) {
t.dontDraw();
Vertex newVert1 = vectorIntersectPlane(planePos,insidePoint[1],outsidePoint[0]);
vertices.add(newVert1);
vertices.add(newVert2);
Triangle temp = new Triangle(t.getVertKeys()[0],t.getVertKeys()[1],vertices);
temp.setColor(0,1,t.getAlpha());
triangles.add(temp);
temp = new Triangle(t.getVertKeys()[0],t.getAlpha());
triangles.add(temp);
continue;
}
}
}
解决方法
我发现了问题，没有为新的裁剪三角形提供正确的顶点参考。不管三角形是否在视图内，它们都被赋予了三角形的第一个顶点。