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 Phong Mapping Effect [320x200x256]  Ander Haglund 20.10.96

Эффект плавного затенения по Фонгу, похожий на высвечивание фонариком части изображения.
Phongmapping stuff, draws a phong.



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  {Phongmapping by Ander Haglund} {I'll try to explain. This is a method that I think is called phongmapping. First you need a "real" texture mapper. With real I mean that you must be able to use any U and V value for every corner, not just the whole texture. Just so you know: U and V is X and Y in "texture space" so there are no missunderstandings. Then you make calculate a phongmap. It should look like a lot of circles going from black in to the object color to white. Something like this: 00000111100000 00112233221100 01234455443210 12345677654321 12345677654321 01234455443210 00112233221100 00000111100000 Where 0-5 is black to object color and 6-7 is object color to white. I use a phongmap that is 256*256 beacuse it's easy to use with the texture-mapper and it's 64kb (65536 bytes). Of course you should use more than just 7 colors in the phongmap... Now, how do we calculate the texture? It's simple! Just scan trough the texture and check the length to the center of the texture. A short example, this is using a palette that's 128 colors. } uses crt; const palwhite = 20; {How many of the 128 colors that should be white} var phongmap : pointer; x,y : integer; c,i : byte; procedure setpal(c,r,g,b : byte);assembler; asm mov dx,3C8h;mov al,c;out dx,al;inc dx;mov al,r;out dx,al;mov al,g out dx,al;mov al,b;out dx,al;end; procedure makepal(objr,objg,objb : byte); begin {black to object color} for i := 0 to 127-palwhite do setpal(i,(objr*i) div (127-palwhite),(objg*i) div (127-palwhite), (objb*i) div (127-palwhite)); {object color to white} for i := 0 to palwhite do setpal(i+127-palwhite,objr+((63-objr)*i) div palwhite, objg+((63-objg)*i) div palwhite,objb+((63-objb)*i) div palwhite); end; function length(x1,y1,x2,y2 : longint) : word; begin length := round(sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2))); end; begin write('Calculating...'); getmem(phongmap,65535); for y := 0 to 127 do for x := 0 to 127 do begin c := length(x,y,128,128); {Get length} if c > 127 then c := 127; c := 127-c; {Revert the color so you don't get black in the middle} mem[seg(phongmap^):y shl 8+x] := c; mem[seg(phongmap^):(255-y) shl 8+x] := c; mem[seg(phongmap^):y shl 8+(255-x)] := c; mem[seg(phongmap^):(255-y) shl 8+(255-x)] := c; end; asm mov ax,13h int 10h end; makepal(32,16,63); {This is going to be a blue-magenta object} {Draw the phongmap (in scale 1:2)} for y := 0 to 127 do for x := 0 to 127 do mem[$A000:x+y shl 8+y shl 6] := mem[seg(phongmap^):x shl 1+y shl 9]; repeat until keypressed; asm mov ax,3h int 10h end; end. When you got the phongmap and palette right you must fix some with the object. First you read the object from disk (No object that fits in a const looks good with phong, you can't phongmap a cube or simular). I sugest that you that you read a object from 3D studio, the face for example, that's one of the objects I'm using. When you read the object you calculate the face normals. Like this: const maxp = 900; {Max points} maxpl = 900; {Max planes} var points : array[0..maxp,0..2] of integer; planes : array[0..maxpl,0..2] of word; pnormals : array[0..maxpl,0..2] of integer; {Plane normals} {It's these normals we are going to use:} normals : array[0..maxp,0..2] of integer; {Corner or edge normals} maxpoint,maxpoint : word; {The actual numbers of points and planes} i,a,n : word; rx1,ry1,rz1,rx2,ry2,rz2 : integer; rx,ry,rz,l : real; begin readobject; {This one is up to you to make, I don't know how you store your objects...} for i := 0 to maxplane do begin rx1 := points[planes[i,1],0]-points[planes[i,0],0]; ry1 := points[planes[i,1],1]-points[planes[i,0],1]; rz1 := points[planes[i,1],2]-points[planes[i,0],2]; rx2 := points[planes[i,2],0]-points[planes[i,0],0]; ry2 := points[planes[i,2],1]-points[planes[i,0],1]; rz2 := points[planes[i,2],2]-points[planes[i,0],2]; {Calculate plane normal (you should know this if you made a flat shading)} pnormals[i,0] := ry1*rz2-ry2*rz1; pnormals[i,1] := rz1*rx2-rz2*rx1; pnormals[i,2] := rx1*ry2-rx2*ry1; end; for i := 0 to maxpoint do begin {Reset all variabels} rx := 0;ry := 0;rz := 0;n := 0; for a := 0 to maxplane do {Check if point is in plane} if (planes[a,0] = i) or (planes[a,1] = i) or (planes[a,2] = i) then begin {Add plane normal to corner/edge normal} rx := rx+pnormals[a,0]; ry := ry+pnormals[a,1]; rz := rz+pnormals[a,2]; {Increase numbers of planes} inc(n); end; if n > 0 then begin {n should allways be over 0, otherwise the point isn't used at all} rx := rx/n;ry := ry/n;rz := rz/n; {Calculate average normal for plane} l := sqrt(rx*rx+ry*ry+rz*rz); {Calculate length of normal} if l = 0 then l := 1; {So you don't get divide error} {120 is length of normal (should be 127 but then you get some rounding errors)} {This scales the normals so they have the same length} normals[i,0] := round(rx/l*120); normals[i,1] := round(ry/l*120); normals[i,2] := round(rz/l*120); end; end; end. Then you have come to the actual drawing. First you rotate the points as usual. Then you rotate all normals as mush as you rotated the points. You convert the points to 2d of course but not the normals... Then you sort the polys and the usual stuff. Then commes the drawing of the polys. It's pretty simple actualy. You let the X and Y value of the corners normal be U and V value to the texture-mapper. You must add 128 to the U and V value so you draw from the center of the phongmap. Then you just texturmap the poly using the phongmap as texture. This routine should look something like this: begin [init stuff, calculate phongmap, go to graph mode and so on.] repeat [Rotate points and normals, convert to 2d and sort polys.] for i := 0 to maxplane do {pind[i] is from the sorting routine, just so you know} texture( {X and Y coordinates for the first corner in the poly:} 160+newp[planes[pind[i],0],0],100+newp[planes[pind[i],0],1], {U and V coordinates for the first corner in the poly:} 128+newn[planes[pind[i],0],0],128+newn[planes[pind[i],0],1], {X and Y coordinates for the second corner in the poly and so on...} 160+newp[planes[pind[i],1],0],100+newp[planes[pind[i],1],1], 128+newn[planes[pind[i],1],0],128+newn[planes[pind[i],1],1], 160+newp[planes[pind[i],2],0],100+newp[planes[pind[i],2],1], 128+newn[planes[pind[i],2],0],128+newn[planes[pind[i],2],1]); [Retrace, display picture and clear virtual screen.] until keypressed; [Go back to textmode] end;