DGL • Thema anzeigen - stencil shadow volumes

stencil shadow volumes

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Sascha Willems

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Verfasst: Do Sep 16, 2004 10:42

DGL Member

Registriert: Mo Sep 23, 2002 19:27
Beiträge: 5812
Programmiersprache: C++

Hm, seems you misunterstood that function. It takes your current vertices list and creates a NEW list out of that, where there are no duplicate vertices anymore. Anyway, since I have stencil shadows implemented using 3DS (via a separate unit and class) and this thread is getting messy, I'd be willing to give you my unit, but since I don't want (for now) it to be released to the public, please use it only for learning purposes and don't give it away. If you're interested, please pm me.

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noeska

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Verfasst: Fr Okt 08, 2004 16:43

DGL Member

Registriert: Di Jul 01, 2003 18:59
Beiträge: 887
Wohnort: (The Netherlands)
Programmiersprache: fpc/delphi/java/c#

I need some feedback on the following screenshot (what am i doing wrong?)

I think i need to refine my edge detection routine as it misses one edge, but finds another one?
And it now also looks my stencil is set up wrong again.

Could someone provide some clean feedback as to where is should look?

This is my connectivity routine:

Code:

 
procedure T3DSMesh.SetConnectivity;
var
  A1, A2, B1, B2: GLuint;
  ifaceA, ifaceB, edgeA, edgeB: GLuint;
begin
  for ifaceA := 0 to (FNumIndices div 3)-1 do
      for edgeA := 0 to 2 do
       begin
        Ffaces[ifaceA].neighbour[edgeA] := -1;
       end; 
 
  for ifaceA := 0 to (FNumIndices div 3) -1  do
    for ifaceB := ifaceA + 1 to (FNumIndices div 3) - 1 do
      for edgeA := 0 to 2 do
        if FFaces[ifaceA].neighbour[edgeA] <> 0 then
          for edgeB := 0 to 2 do
            begin
            a1 := Ffaces[ifaceA].vertex[edgeA];
            a2 := Ffaces[ifaceB].vertex[(edgeA+1) mod 3];
            b1 := Ffaces[ifaceA].vertex[edgeB];
            b2 := Ffaces[ifaceB].vertex[(edgeB+1) mod 3];
            if ((a1 = b1) and (a2 = b2)) or ((a1 = b2) and (a2 = b1)) then
              begin
                Ffaces[ifaceA].neighbour[edgeA] := ifaceB;
                Ffaces[ifaceB].neighbour[edgeB] := ifaceA;
              end;
            end;
end;
 

This is my visibility checking routine:

Code:

 
procedure T3DSMesh.PrepareShadows(lp: T3dPoint);
var
  i: gluint;
  side: glfloat;
begin
    if FNumIndices > 0 then
    begin
  //determine if an face is lit by the light or not
  for i := 0 to (fnumIndices DIV 3) -1 do
    begin
    side := FFaces[i].Plane.a*lp.x
           +FFaces[i].Plane.b*lp.y
           +FFaces[i].Plane.c*lp.z;
    if (side > 0) then //hmmm why
      Ffaces[i].visible := true
    else
      Ffaces[i].visible := false;
    end;
  end;
end;
 

On rendering the shadow i use:

Code:

 
  //use lit faces to render the shadow volume
  for i := 0 to (FNumIndices DIV 3) -1 do
    if Ffaces[i].visible then //go through all visible faces...
     begin
      for j := 0 to 1 do
        begin
         k := Ffaces[i].neighbour[j];
         //an edge occurs when the other face is not visible...
         if (k=-1) or (not Ffaces[k].visible) then
          begin
 

I am sorry to make this thread longer, but i need the public feedback

Dateianhänge:

fbp.jpg [ 15.29 KiB | 2063-mal betrachtet ]

_________________
http://3das.noeska.com - create adventure games without programming

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Sascha Willems

Betreff des Beitrags:

Verfasst: Fr Okt 08, 2004 21:25

DGL Member

Registriert: Mo Sep 23, 2002 19:27
Beiträge: 5812
Programmiersprache: C++

Just one quick thought : Have you checked of all normals are correct? If you for example have two coplanar triangles (i.e. every side of the cube), one of the normals may be flipped and that'll cause your shilhouette-detection to think that there is an edge were none should be.

_________________
www.SaschaWillems.de | GitHub | Twitter | GPU Datenbanken (Vulkan, GL, GLES)

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