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renderer3/hrend/math.go

@@ -329,6 +329,18 @@ func (v0 *Vec3f) Scale(s float32) *Vec3f {
 	}
 }
 
+func LerpVec3f(v0 Vec3f, v1 Vec3f, t float32) Vec3f {
+	return Vec3f{
+		X: (1-t)*v0.X + t*v1.X,
+		Y: (1-t)*v0.Y + t*v1.Y,
+		Z: (1-t)*v0.Z + t*v1.Z,
+	}
+}
+
+func LerpF32(a, b, t float32) float32 {
+	return (1-t)*a + t*b
+}
+
 func (v0 *Vec3f) CrossProduct(v1 *Vec3f) *Vec3f {
 	return &Vec3f{
 		X: v0.Y*v1.Z - v0.Z*v1.Y,

renderer3/hrend/render.go

@@ -207,26 +207,9 @@ func BackfaceCull(v1, v2, v3 Vec3f) bool {
 	return (v1.X-v2.X)*(v3.Y-v2.Y)-(v1.Y-v2.Y)*(v3.X-v2.X) >= 0
 }
 
-func PerspectiveAndClip(face Facef, matrix3d *Mat44f) []Facef {
-	outfaces := make([]Facef, 0, 2)
-	var sc Facef
-	var w [3]float32
-	var d [3]float32
-	outers := make([]int, 0, 3)
+func conditionalAddTriangle(sc Facef, w [3]float32, out []Facef) []Facef {
+	// The triangle is fine
 	for i := range 3 {
-		sc[i] = face[i]
-		sc[i].Pos, w[i] = matrix3d.MultiplyPoint3(face[i].Pos)
-		d[i] = sc[i].Pos.Z + w[i]
-		if d[i] < 0 {
-			outers = append(outers, i)
-		}
-	}
-	// Just to test: reject any that have points outside. We don't clip
-	if len(outers) > 0 {
-		return outfaces
-	} else {
-		for i := range 3 {
-			//sc[i]
 		if w[i] != 1 {
 			sc[i].Pos.X /= w[i]
 			sc[i].Pos.Y /= w[i]
@@ -235,12 +218,87 @@ func PerspectiveAndClip(face Facef, matrix3d *Mat44f) []Facef {
 	}
 	// Backface culling: no need to do anything with triangles facing the wrong way
 	if EdgeFunction(sc[0].Pos, sc[1].Pos, sc[2].Pos) <= 0 {
-			outfaces = append(outfaces, sc)
+		out = append(out, sc)
 	}
-		//outfaces[facei] = sc
-		//facei += 1
+
+	return out
+}
+
+func PerspectiveAndClip(face Facef, matrix3d *Mat44f) []Facef {
+	outfaces := make([]Facef, 0, 2)
+	var sc Facef
+	var w [3]float32
+	var d [3]float32
+	outers := make([]int, 0, 3)
+	inners := make([]int, 0, 3)
+	for i := range 3 {
+		sc[i] = face[i]
+		sc[i].Pos, w[i] = matrix3d.MultiplyPoint3(face[i].Pos)
+		d[i] = sc[i].Pos.Z + w[i]
+		if d[i] < 0.001 {
+			outers = append(outers, i)
+		} else {
+			inners = append(inners, i)
+		}
+	}
+
+	if len(outers) == 2 { // The one triangle thing
+		ai := inners[0]
+		bi := outers[0]
+		ci := outers[1]
+
+		// Calc how far along we are on each of these lines. These are the new points
+		tab := d[ai] / (d[ai] - d[bi])
+		tac := d[ai] / (d[ai] - d[ci])
+
+		// The two points that aren't a need to be the interpolated values
+		sc[bi].Pos = LerpVec3f(sc[ai].Pos, sc[bi].Pos, tab)
+		sc[ci].Pos = LerpVec3f(sc[ai].Pos, sc[ci].Pos, tac)
+		w[bi] = LerpF32(w[ai], w[bi], tab)
+		w[ci] = LerpF32(w[ai], w[ci], tac)
+
+		outfaces = conditionalAddTriangle(sc, w, outfaces)
+	} else if len(outers) == 1 { // The two triangle thing, two new corners
+		ai := outers[0]
+		bi := inners[0]
+		ci := inners[1]
+
+		tab := d[ai] / (d[ai] - d[bi])
+		tac := d[ai] / (d[ai] - d[ci])
+		wa := w[ai]
+
+		// This time, we're generating two new points.
+		sct := sc
+
+		// Only ONE point needs to be modified: the one outer. Remember that
+		// tab and tac are the distance to that point itself, so a still needs
+		// to be the first value here
+		sct[ai].Pos = LerpVec3f(sc[ai].Pos, sc[bi].Pos, tab)
+		w[ai] = LerpF32(w[ai], w[bi], tab)
+		outfaces = conditionalAddTriangle(sct, w, outfaces)
+
+		// Now that we've replaced the far point, we also need to replace
+		// the original B point that we used, since that's part of the other
+		// triangle. But simply replacing it will make the triangle invisible,
+		// since it inverts the winding order (I think)
+		sct[bi].Pos = LerpVec3f(sc[ai].Pos, sc[ci].Pos, tac)
+		w[bi] = LerpF32(wa, w[ci], tac)
+		// Now swap the a and b
+		w[ai], w[bi] = w[bi], w[ai]
+		sct[ai], sct[bi] = sct[bi], sct[ai]
+		outfaces = conditionalAddTriangle(sct, w, outfaces)
+
+		/*
+			sc2[ai].Pos = LerpVec3f(sc2[ai].Pos, sc2[ci].Pos, tac)
+			w[ai] = LerpF32(w[ai], w[ci], tac)
+			//outfaces = conditionalAddTriangle(sc2, w, outfaces)
+		*/
+
+	} else if len(outers) != 3 { // Output the face itself, no modification
+		outfaces = conditionalAddTriangle(sc, w, outfaces)
+	}
+
 	return outfaces
-	}
 
 	// TODO: Now that we're here doing it like this, might as well remove faces
 	// that are fully outside the other clipping zones. No need to do actual clipping...