• Create Account

### #Actualjuddo

Posted 07 November 2012 - 09:25 PM

hello all,

i am reading vertex data from a game file that stores a character model in triangle strips (ps2 game, hence why triangle strips are used). i did concider converting the triangle strips into vertex indexing to help ease the pain of calculating my normals at runtime, but still would like some help calculating normals for triangle strips.

i recently read on here that triangle strips flip cw/ccw culling every triangle if backface culling is on. below is my code for calculating normals at the moment;

[source lang="cpp"] float vu[3]; float vv[3]; float cp[3]; float result; for (int k = 0; k < nvertices; k++) { vu[0] = vertices[k + 1][0] - vertices[k][0]; vu[1] = vertices[k + 1][1] - vertices[k][1]; vu[2] = vertices[k + 1][2] - vertices[k][2]; vv[0] = vertices[k + 1][0] - vertices[k + 2][0]; vv[1] = vertices[k + 1][1] - vertices[k + 2][1]; vv[2] = vertices[k + 1][2] - vertices[k + 2][2]; cp[0] = (vu[2] * vv[1]) - (vu[1] * vv[2]); cp[1] = (vu[0] * vv[2]) - (vu[2] * vv[0]); cp[2] = (vu[1] * vv[0]) - (vu[0] * vv[1]); result = (float)sqrt((cp[0]*cp[0]) + (cp[1]*cp[1]) + (cp[2]*cp[2])); if (result == 0.0f) result = 1.0f; normals[k][0] = cp[0] / result; normals[k][1] = cp[1] / result; normals[k][2] = cp[2] / result; }[/source]

when i run my program with the above code, i see the following;

&&

you can see on this side shot that i can see through the model (less than desireable.) at the moment i am iterating through every vertex, do i need an offset in my loop to calculate the next triangle or next vertex? it looks like the normals are facing away from each other...

and this is the drawing code...

[source lang="cpp"]glPushMatrix(); glTranslatef(posx_, posy_, posz_); glRotatef(90.0f, 0, 0, 1); glRotatef(turnrate_, 1, 0, 0); glBegin(GL_TRIANGLE_STRIP); for (int i = 0; i < model_.nvertices; i++) { glNormal3f(model_.normals[i][0], model_.normals[i][1], model_.normals[i][2]); glVertex3f(model_.vertices[i][0], model_.vertices[i][1], model_.vertices[i][2]); } glEnd();glPopMatrix();[/source]

best regards,

justin

### #1juddo

Posted 07 November 2012 - 08:44 PM

hello all,

i am reading vertex data from a game file that stores a character model in triangle strips (ps2 game, hence why triangle strips are used). i did concider converting the triangle strips into vertex indexing to help ease the pain of calculating my normals at runtime, but still would like some help calculating normals for triangle strips.

i recently read on here that triangle strips flip cw/ccw culling every triangle if backface culling is on. below is my code for calculating normals at the moment;

[source lang="cpp"] float vu[3]; float vv[3]; float cp[3]; float result; for (int k = 0; k < nvertices; k++) { vu[0] = vertices[k + 1][0] - vertices[k][0]; vu[1] = vertices[k + 1][1] - vertices[k][1]; vu[2] = vertices[k + 1][2] - vertices[k][2]; vv[0] = vertices[k + 1][0] - vertices[k + 2][0]; vv[1] = vertices[k + 1][1] - vertices[k + 2][1]; vv[2] = vertices[k + 1][2] - vertices[k + 2][2]; cp[0] = (vu[2] * vv[1]) - (vu[1] * vv[2]); cp[1] = (vu[0] * vv[2]) - (vu[2] * vv[0]); cp[2] = (vu[1] * vv[0]) - (vu[0] * vv[1]); result = (float)sqrt((cp[0]*cp[0]) + (cp[1]*cp[1]) + (cp[2]*cp[2])); if (result == 0.0f) result = 1.0f; normals[k][0] = cp[0] / result; normals[k][1] = cp[1] / result; normals[k][2] = cp[2] / result; }[/source]

when i run my program with the above code, i see the following;

&&

you can see on this side shot that i can see through the model (less than desireable.) at the moment i am iterating through every vertex, do i need an offset in my loop to calculate the next triangle or next vertex? it looks like the normals are facing away from each other...