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preparing for hidden line removal

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Irmen de Jong 2020-09-18 22:39:30 +02:00
parent 5d900800f2
commit 63a653cdf0
1 changed files with 67 additions and 18 deletions
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85
examples/cx16/cobramk3-gfx.p8
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@ -147,31 +147,80 @@ main {
sub draw_lines_hiddenremoval() {
; complex routine that draws the ship model based on its faces
; where it uses the surface normals to determine visibility.
; TODO use a pointer to the edges instead of indexing
; TODO use a pointer to the edges and points instead of indexing
memset(edgestodraw, shipdata.totalNumberOfEdges, true)
ubyte @zp edgeIdx = 0
ubyte @zp i
for i in shipdata.totalNumberOfFaces -1 downto 0 {
ubyte e1
ubyte e2
ubyte e3
e1 = shipdata.facesEdges[edgeIdx]
edgeIdx ++
e2 = shipdata.facesEdges[edgeIdx]
edgeIdx ++
e3 = shipdata.facesEdges[edgeIdx]
edgeIdx ++
draw_edge(e1)
draw_edge(e2)
while e3!=255 {
draw_edge(e3)
e3 = shipdata.facesEdges[edgeIdx]
ubyte @zp pointIdx = 0
ubyte faceNumber
for faceNumber in shipdata.totalNumberOfFaces -1 downto 0 {
if facing_away(pointIdx) {
; don't draw this face, fast-forward over the edges and points
edgeIdx += 3 ; every face hast at least 3 edges
while shipdata.facesEdges[edgeIdx]!=255 {
edgeIdx++
}
edgeIdx++
pointIdx += 3 ; every face has at least 3 points
while shipdata.facesPoints[pointIdx]!=255 {
pointIdx++
}
pointIdx++
} else {
; draw this face
ubyte @zp e1 = shipdata.facesEdges[edgeIdx]
edgeIdx ++
ubyte @zp e2 = shipdata.facesEdges[edgeIdx]
edgeIdx ++
ubyte @zp e3 = shipdata.facesEdges[edgeIdx]
edgeIdx ++
if edgestodraw[e1]
draw_edge(e1)
if edgestodraw[e2]
draw_edge(e2)
while e3!=255 {
if edgestodraw[e3]
draw_edge(e3)
e3 = shipdata.facesEdges[edgeIdx]
edgeIdx ++
}
; skip the rest of the facesPoints, we don't need them here anymore
pointIdx += 3 ; every face has at least 3 points
while shipdata.facesPoints[pointIdx]!=255 {
pointIdx++
}
pointIdx++
}
}
}
sub facing_away(ubyte edgePointsIdx) -> ubyte {
; todo hidden line removal check
; ubyte p1x = shipdata.
;
; word normal_z
;
; def normal_z(self, points: Tuple) -> float:
; p1 = self.rotated_coords[points[0]]
; p2 = self.rotated_coords[points[1]]
; p3 = self.rotated_coords[points[2]]
; # So for a triangle p1, p2, p3, if the vector U = p2 - p1 and the vector V = p3 - p1
; # then the normal N = U * V and can be calculated by:
; # Nx = UyVz - UzVy
; # Ny = UzVx - UxVz
; # Nz = UxVy - UyVx
; ux = p2[0]-p3[0]
; uy = p2[1]-p3[1]
; vx = p1[0]-p3[0]
; vy = p1[1]-p3[1]
; return ux*vy - uy*vx
return 0
}
ubyte[shipdata.totalNumberOfEdges] edgestodraw
sub draw_edge(ubyte edgeidx) {
; todo: keep track of edges that are already drawn, don't redraw
edgestodraw[edgeidx] = false
ubyte vFrom = shipdata.edgesFrom[edgeidx]
ubyte vTo = shipdata.edgesTo[edgeidx]
word persp1 = 200 + rotatedz[vFrom]/256