DGL • Thema anzeigen - stencil shadow volumes

stencil shadow volumes

Moderator: DGL-Team

Seite 3 von 4

[ 48 Beiträge ]

Gehe zu Seite Vorherige 1, 2, 3, 4 Nächste

Druckansicht

Vorheriges Thema | Nächstes Thema

Autor

Nachricht

Magellan

Betreff des Beitrags:

Verfasst: So Sep 12, 2004 20:10

DGL Member

Registriert: Di Nov 26, 2002 22:12
Beiträge: 259
Wohnort: Dresden

Now everything works fine and the frame rates are acceptable.

_________________
Nichts auf der Welt ist so gerecht verteilt wie der Verstand. Denn jederman ist überzeugt, dass er genug davon habe.
Rene Descartes, frz. Mathematiker u. Philosoph, 1596-1650

Nach oben

noeska

Betreff des Beitrags:

Verfasst: So Sep 12, 2004 22:33

DGL Member

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

240fps with shadows, ok i need to work some more on my code. Are you using special ways rendering like vbo's or are they plain old glvertex3f's you use.

So ati handles setting up stencil buffers differently then nvidia? Is there a generic way that works on both? Or were you using a special ati extension?

By looking at your demo the zfail method is the way to get shadows always right. I should look into that also.

Like is said in the beginning, some things start simple.... , but things are starting to look good. A side point is that the gl3ds can be cleaned up some more and becomes easier to read as it now uses faces, they were there before, but not so easy to access. So this things turns to become a win win situation. But then again when you think you are finished some more problem can come in the way.

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

Nach oben

Sascha Willems

Betreff des Beitrags:

Verfasst: So Sep 12, 2004 22:35

DGL Member

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

No, I use plain ol' glVertex-calls (aka immediate mode) in that demo, so nothing special there. And as for setting stencil up : I didn't do anything special to ATI, I just forgot to ask for a pixelformat with stencil bits, and ATI cards then give you (if you request 24 depth and 32 color bits) automatically 8 bits of stencil, NV cards don't (as it seems).

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

Nach oben

noeska

Betreff des Beitrags:

Verfasst: Mo Sep 13, 2004 18:53

DGL Member

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

i am running out of ideas and shadow are still not working ok. It seems that once meshes overlap holes start to occur in the shadows.

here is my main render routine

Code:

 
glClear(GL_COLOR_BUFFER_BIT or GL_DEPTH_BUFFER_BIT or GL_STENCIL_BUFFER_BIT);   
  glLoadIdentity();
 
  camera.Render; //set the camera position
 
  //set light position
  glLightfv(GL_LIGHT0, GL_POSITION, @lp); //position light
 
  //get the light position
  objlightpos2.x:=lp[0];
  objlightpos2.y:=lp[1];
  objlightpos2.z:=lp[2];
  objlightpos2.w:=lp[3];
 
  // Get the inverse model matrix
  glPushMatrix;
    glLoadIdentity;
    glGetFloatv(GL_MODELVIEW_MATRIX, @InvMatrix);
  glPopMatrix;
  //Get the object space light vector
  ObjLightPos2 := vectortransform4f(objlightpos2,InvMatrix);
 
  // Draw the light
  glDisable(GL_LIGHTING);
  glPushMatrix();
    glTranslatef(LP[0], LP[1], LP[2]);
    glColor3f(1, 1, 0);
    gluSphere(LightObj, 0.2, 8, 8);
  glPopMatrix();
    glEnable(GL_LIGHTING);
  //now on to rendering...
  glrotatef(270,1,0,0); //rotate the scene...
 
//fill the depth buffer (ambient pass)
glenable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
glEnable(GL_CULL_FACE);
glCullFace(GL_BACK);
//ambientmode:=true;
drawscene;
 
//prepare for shadows
glDepthMask(FALSE);
glEnable(GL_BLEND);
glBlendFunc(GL_ONE,GL_ONE);
 
//for each light
glDisable(GL_LIGHT0);
glClear(GL_STENCIL_BUFFER_BIT);
glColorMask(FALSE,FALSE,FALSE,FALSE);
glEnable(GL_STENCIL_TEST);
glStencilFunc(GL_ALWAYS, 0, byte(not 0));
glStencilMask(byte(not 0));
 
makeshadows; //determine face visibility...
 
//zfail
glEnable(GL_CULL_FACE);
glCullFace(GL_FRONT);
glStencilOp(GL_KEEP, GL_INCR_WRAP, GL_KEEP);
drawshadows;
 
glCullFace(GL_BACK);
glStencilOp(GL_KEEP, GL_DECR_WRAP, GL_KEEP);
drawshadows;
 
glEnable(GL_LIGHT0);
//end for each light
 
glCullFace(GL_BACK);
//draw diffuse part
glStencilFunc(GL_EQUAL, 0, byte(not 0));
glStencilOp(GL_KEEP, GL_KEEP, GL_INCR);
gldepthfunc(GL_EQUAL);
glColorMask(TRUE,TRUE,TRUE,TRUE);
//ambientmode:=false;
drawscene;
 
//restore render settings
glDepthFunc(GL_LESS);
glDisable(GL_BLEND);
glDisable(GL_STENCIL_TEST);
glDepthMask(TRUE);
 
//render the gui
gldisable(GL_TEXTURE_2D);
glActiveTexture(GL_TEXTURE0); //go back to texture0 (just to be save)
 
rendergui;
 
//Flush the OpenGL Buffer
glFlush(); //is it needed?
 

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

Nach oben

Sascha Willems

Betreff des Beitrags:

Verfasst: Mo Sep 13, 2004 21:24

DGL Member

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

Code:

glStencilFunc(GL_ALWAYS, 0, byte(not 0));

That's wrong. It should be $FFFFFFFF for the last parameter.

Code:

//zfail
glEnable(GL_CULL_FACE);
glCullFace(GL_FRONT);
glStencilOp(GL_KEEP, GL_INCR_WRAP, GL_KEEP);
drawshadows;
 
glCullFace(GL_BACK);
glStencilOp(GL_KEEP, GL_DECR_WRAP, GL_KEEP);
drawshadows; 

If you use Z-Pass, then you need to cap your shadow volumes. Otherwise you'll the the effect described, that objectss seem to make holes in the shadow. So either go for Z-Fail (which won't work if you enter the volume) or cap your shadow volumes (front and back-cap needed). Capping should be straight forward, as you normally only need to duplicate all light-facing triangles for the front-cap and extrude those for the back-cap. That's not the best method, but it's the easiest.

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

Nach oben

noeska

Betreff des Beitrags:

Verfasst: Mi Sep 15, 2004 10:00

DGL Member

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

for the moment the shadows seem to get only worse. I post the complete project here. Thanks in advance for your feedback on it. Maybe i am doing things all wrong or it is just an stencil mistake.

Dateianhänge:

Dateikommentar: the 3ds mesh used with texture (made by sos)

shadmesh.zip [229.16 KiB]
309-mal heruntergeladen
Dateikommentar: volume shadow test program source

shadowstest.zip [35.69 KiB]
303-mal heruntergeladen

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

Nach oben

Sascha Willems

Betreff des Beitrags:

Verfasst: Mi Sep 15, 2004 12:27

DGL Member

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

It seems that the biggest (maybe THE) problem right now is that your silhouette determination is not working as it should. I've changed your demo to show me the silhouette edges as lines, and directly saw that there's a problem :
Bild

I've marked some errors with red arrows. A silhouette edge should only occure where a border is between a triangle that faces the light and one that doesn't face the light. But as you can see, you have also silhouette edges between two triangles that are both facing the light. Those edges also get extruded and change the count of the stencil value, which will cause wrong results. So check your silhouette determination. I stronlgy suggest you to look at the demo from delphi3d.net, as he does all necessary things with an ASE-file and that's not hard to change to 3DS. One thing he does that you don't is for example the optimization of the meshes for shadow volume generation. Without that, your scene will also generate errors.

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

Nach oben

noeska

Betreff des Beitrags:

Verfasst: Mi Sep 15, 2004 13:41

DGL Member

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

another question if i use zfail can i then forget about zpass? Or do i need both and need to determine which one to use per mesh and lightpos?

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

Nach oben

Sascha Willems

Betreff des Beitrags:

Verfasst: Mi Sep 15, 2004 13:45

DGL Member

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

No, you can only use zFail, cause that works all the time. But you normally determine if you need zFail or zPass and only render zPass when in the shadowvolume. That's because zFail eats more performance, as you need to cap the volume, what also results in more fillrate getting burned. But you normally can get away (I do that too as of now) with only zFail.

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

Nach oben

noeska

Betreff des Beitrags:

Verfasst: Mi Sep 15, 2004 14:08

DGL Member

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

This is how things look now:

How do you render the outlines? Replacing the gl_triangles wit gl_lines in endshadow? I seem to get lines and not the triangle like things you get (bet then i changed my code in between) I redownload the version i uploaded...

Dateianhänge:

Dateikommentar: Wrong stencil count

wrong.jpg [ 48.68 KiB | 5881-mal betrachtet ]

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

Nach oben

Sascha Willems

Betreff des Beitrags:

Verfasst: Mi Sep 15, 2004 14:21

DGL Member

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

In T3DSMesh.CastShadow, I changed this :

Code:

glLineWidth(5);
glEnable(GL_LINE_SMOOTH);
glbegin(GL_LINES);
...
glVertex3f(fvertex[p1].x, fvertex[p1].y, fvertex[p1].z);
glVertex3f(fvertex[p2].x, fvertex[p2].y, fvertex[p2].z);
 

And removed all other vertex calls. This will show you all edges in that function.

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

Nach oben

noeska

Betreff des Beitrags:

Verfasst: Mi Sep 15, 2004 14:31

DGL Member

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

ok, i see them now also, now i have some feedback on trying to fix visibility....

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

Nach oben

noeska

Betreff des Beitrags:

Verfasst: Mi Sep 15, 2004 17:47

DGL Member

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

how do i determine if face is visible:

First i determine if a face is lit by the light or not:

Code:

 
procedure T3DSMesh.PrepareShadows(lp: T4dPoint);
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 + FFaces[i].Plane.d*lp.w; 
    if side > 0 then
     begin
      Ffaces[i].visible := true
     end
      else
     begin
      Ffaces[i].visible := false;
     end;
    end;
  end;
end;
 

Now for the lit faces i have to find the neighbouring faces that are not lit. Then i found an edge. That has to be rendered. This is what i am supposed to be doing on drawing the siloute i it looks ok now but still the shadows look wrong.

This is my changed castshadow routine:

Code:

 
procedure T3DSMesh.CastShadow(lp: T4dPoint);
var
  i, j, k, jj: GLuint;
  p1, p2: GLuint;
  v1, v2: T3DPoint;
begin
  if FShadDisplaylist > 0 then glcalllist(FShadDisplaylist)
  else
  begin
 
    if FNumIndices > 0 then
    begin
 
    glbegin(GL_QUADS);
  j:=0;
  //use lit faces to render the shadow volume
  for i := 0 to (FNumIndices DIV 3) - 1 do
    if Ffaces[i].visible then
      for j := 0 to 1 do
        begin
         k := Ffaces[i].neighbour[j];
         //an edge occurs when the other face is not visible...
         if (not Ffaces[k-1].visible) then
          begin
          p1 := Ffaces[i].vertex[j];
          jj := (j+1) mod 3;
          p2 := Ffaces[i].vertex[jj];
 
          v1.x := (fVertex[p1].x - lp.x) * extend;
          v1.y := (fVertex[p1].y - lp.y) * extend;
          v1.z := (fVertex[p1].z - lp.z) * extend;
          v2.x := (fVertex[p2].x - lp.x) * extend;
          v2.y := (fVertex[p2].y - lp.y) * extend;
          v2.z := (fVertex[p2].z - lp.z) * extend;
 
          glVertex4f(fvertex[p2].x, fvertex[p2].y, fvertex[p2].z,1.0);
          glVertex4f(fvertex[p1].x, fvertex[p1].y, fvertex[p1].z,1.0);
          glVertex4f(fvertex[p1].x + v1.x, fvertex[p1].y + v1.y, fvertex[p1].z + v1.z,0.0);
          glVertex4f(fvertex[p2].x + v2.x, fvertex[p2].y + v2.y, fvertex[p2].z + v2.z,0.0);
 
          end;
        end;
 
        glend;
   end;
   end;
end;
 

zfail still looks wrong
zpass almost looks good

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

Nach oben

Sascha Willems

Betreff des Beitrags:

Verfasst: Mi Sep 15, 2004 22:07

DGL Member

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

Have you implemented the optimizations for the mesh I've posted on the first page? Otherwise you WILL get shadow errors, as 3DS sometimes have duplicate vertices in them, and the function I posted fixes that.

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

Nach oben

noeska

Betreff des Beitrags:

Verfasst: Mi Sep 15, 2004 23:08

DGL Member

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

it did not help, but (like everything

) i may have implemented it wrong. Here it is:

Code:

 
function glCompareVertex(v1,v2: T3DPoint): boolean;
begin
  Result := (Abs(v1.x - v2.x) < 0.0001) and
            (Abs(v1.y - v2.y) < 0.0001) and
            (Abs(v1.z - v2.z) < 0.0001);// and
//            (Abs(1.0 - 1.0) < 0.0001);           //??
end;
 
function T3DSMesh.FindVertex(const v: T3DPoint): Cardinal;
  var
    ivert: Integer;
  begin
    Result := 0;
    for ivert := 0 to FNumIndices-1 do
    begin
      if glCompareVertex(v, fvertex[ivert]) then
      begin
        Result := ivert;
        Exit;
      end;
    end;
  end;
 
procedure TAll3DSMesh.OptimizeTriangleList;
var
  itri: Integer;
  m: integer;
begin
  for m := 0 to FNumMeshes - 1 do
  begin
    if FMesh[m].FNumIndices > 0 then
for itri := 0 to (Fmesh[m].FnumIndices div 3) -1 do
begin
Fmesh[m].fFaces[itri].vertex[0] := Fmesh[m].FindVertex(Fmesh[m].Fvertex[Fmesh[m].fFaces[itri].vertex[0]]);
Fmesh[m].fFaces[itri].vertex[1] := Fmesh[m].FindVertex(Fmesh[m].Fvertex[Fmesh[m].fFaces[itri].vertex[1]]);
Fmesh[m].fFaces[itri].vertex[2] := Fmesh[m].FindVertex(Fmesh[m].Fvertex[Fmesh[m].fFaces[itri].vertex[2]]);
end;
end;
end;
 

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

Nach oben

Seite 3 von 4

[ 48 Beiträge ]

Gehe zu Seite Vorherige 1, 2, 3, 4 Nächste

Foren-Übersicht » English » English Programming Forum

Wer ist online?

Mitglieder in diesem Forum: 0 Mitglieder und 14 Gäste

Du darfst keine neuen Themen in diesem Forum erstellen.
Du darfst keine Antworten zu Themen in diesem Forum erstellen.
Du darfst deine Beiträge in diesem Forum nicht ändern.
Du darfst deine Beiträge in diesem Forum nicht löschen.
Du darfst keine Dateianhänge in diesem Forum erstellen.