PfhorSlayer

04-24-2003, 02:31 PM

Hello, all. I'm trying to implement stencil shadows in a project I'm working on, using ARB vertex shaders, and I've run into some trouble. I'm following this (http://www.gamasutra.com/features/20021011/lengyel_03.htm) article on Gamasutra, and it does not seem to be working.

Before rendering the shadow volume (both front and back faces), I enable my vertex program, which is as follows:

!!ARBvp1.0

ATTRIB vPos = vertex.position;

OUTPUT oPos = result.position;

PARAM lPos = program.env[0];

TEMP temp;

ADD temp.xyz, vPos, -lPos;

MAD temp, vPos.w, lPos, temp;

DP4 oPos.x, state.matrix.mvp.row[0], temp;

DP4 oPos.y, state.matrix.mvp.row[1], temp;

DP4 oPos.z, state.matrix.mvp.row[2], temp;

DP4 oPos.w, state.matrix.mvp.row[3], temp;

END

My understanding is that this program will extrude vertices with a zero W component, and do nothing to vertices with a one W component.

When rendering the shadow volume, I do:

glVertex4f (verts[1][0], verts[1][1], verts[1][2], 1);

glVertex4f (verts[0][0], verts[0][1], verts[0][2], 1);

glVertex4f (verts[0][0], verts[0][1], verts[0][2], 0);

glVertex4f (verts[1][0], verts[1][1], verts[1][2], 0);

Where the verts array holds the coordinates of the edge that is being extruded.

Before drawing these shadow volumes, I also do:

glProgramEnvParameter4fARB (GL_VERTEX_PROGRAM_ARB, 0, lightvec[0], lightvec[1], lightvec[2], 1.0f);

Where lightvec holds the location of the light I'm using to create the shadow volume.

Nothing actually shows up when using the vertex shader. http://www.opengl.org/discussion_boards/ubb/frown.gif

When I used the following code to calculate the extrusion of the points by hand, it worked. (I already did glVertex3f for the first two, unextruded points)

Vector d1, d2;

d1 = verts[0] - lightvec;

d2 = verts[1] - lightvec;

d1.Normalize ();

d2.Normalize ();

d1 = d1 * 10000;

d2 = d2 * 10000;

glVertex3fv (d1);

glVertex3fv (d2);

Any assistance here would be very much appreciated!

Before rendering the shadow volume (both front and back faces), I enable my vertex program, which is as follows:

!!ARBvp1.0

ATTRIB vPos = vertex.position;

OUTPUT oPos = result.position;

PARAM lPos = program.env[0];

TEMP temp;

ADD temp.xyz, vPos, -lPos;

MAD temp, vPos.w, lPos, temp;

DP4 oPos.x, state.matrix.mvp.row[0], temp;

DP4 oPos.y, state.matrix.mvp.row[1], temp;

DP4 oPos.z, state.matrix.mvp.row[2], temp;

DP4 oPos.w, state.matrix.mvp.row[3], temp;

END

My understanding is that this program will extrude vertices with a zero W component, and do nothing to vertices with a one W component.

When rendering the shadow volume, I do:

glVertex4f (verts[1][0], verts[1][1], verts[1][2], 1);

glVertex4f (verts[0][0], verts[0][1], verts[0][2], 1);

glVertex4f (verts[0][0], verts[0][1], verts[0][2], 0);

glVertex4f (verts[1][0], verts[1][1], verts[1][2], 0);

Where the verts array holds the coordinates of the edge that is being extruded.

Before drawing these shadow volumes, I also do:

glProgramEnvParameter4fARB (GL_VERTEX_PROGRAM_ARB, 0, lightvec[0], lightvec[1], lightvec[2], 1.0f);

Where lightvec holds the location of the light I'm using to create the shadow volume.

Nothing actually shows up when using the vertex shader. http://www.opengl.org/discussion_boards/ubb/frown.gif

When I used the following code to calculate the extrusion of the points by hand, it worked. (I already did glVertex3f for the first two, unextruded points)

Vector d1, d2;

d1 = verts[0] - lightvec;

d2 = verts[1] - lightvec;

d1.Normalize ();

d2.Normalize ();

d1 = d1 * 10000;

d2 = d2 * 10000;

glVertex3fv (d1);

glVertex3fv (d2);

Any assistance here would be very much appreciated!