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Alex
Alex
  • 103
  • 3

EDIT ----------------------------------------------------------------------------------

Thank you Zacharmarz for your guidance, I eventually got the code working with vertexArrays (since the regular array was causing the exception due to unknown size of vertices).... after all this work I was expecting an improvement in performance but my frame rate is almost half what it was when rendering twice with immediate mode.... Maybe I'm doing something extra here? I managed to implement a std::vector collection like recommended:

    for(int i = 0; i < numTriangles; i++) {
        MD2Triangle* triangle = triangles + i;
        for(int j = 0; j < 3; j++) {
            MD2Vertex* v1 = frame1->vertices + triangle->vertices[j];
            MD2Vertex* v2 = frame2->vertices + triangle->vertices[j];
            Vec3f pos = v1->pos * (1 - frac) + v2->pos * frac;
            Vec3f normal = v1->normal * (1 - frac) + v2->normal * frac;
            if (normal[0] == 0 && normal[1] == 0 && normal[2] == 0) {
                normal = Vec3f(0, 0, 1);
            }
            

            normals.push_back(normal[0]);
            normals.push_back(normal[1]);
            normals.push_back(normal[2]);

            MD2TexCoord* texCoord = texCoords + triangle->texCoords[j];
            textCoords.push_back(texCoord->texCoordX);
            textCoords.push_back(texCoord->texCoordY);

            vertices.push_back(pos[0]);
            vertices.push_back(pos[1]);
            vertices.push_back(pos[2]);
        }

    }


    glEnableClientState(GL_NORMAL_ARRAY);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);
    glEnableClientState(GL_VERTEX_ARRAY);

    glNormalPointer(GL_FLOAT, 0, &normals[0]);
    glTexCoordPointer(2, GL_FLOAT, 0, &textCoords[0]); 
    glVertexPointer(3, GL_FLOAT, 0, &vertices[0]);



    glDrawArrays(GL_TRIANGLES, 0, vertices.size()/3);

                                    
    glDisableClientState(GL_VERTEX_ARRAY);  // disable vertex arrays
    glDisableClientState(GL_TEXTURE_COORD_ARRAY);
    glDisableClientState(GL_NORMAL_ARRAY);

    vertices.clear();
    textCoords.clear();
    normals.clear();

Is there something extra that I am doing here? Cos this is really meant to be more efficient that glBegin()/End(), right?

Thanks for your time and help!

EDIT ----------------------------------------------------------------------------------

Thank you Zacharmarz for your guidance, I eventually got the code working with vertexArrays (since the regular array was causing the exception due to unknown size of vertices).... after all this work I was expecting an improvement in performance but my frame rate is almost half what it was when rendering twice with immediate mode.... Maybe I'm doing something extra here? I managed to implement a std::vector collection like recommended:

    for(int i = 0; i < numTriangles; i++) {
        MD2Triangle* triangle = triangles + i;
        for(int j = 0; j < 3; j++) {
            MD2Vertex* v1 = frame1->vertices + triangle->vertices[j];
            MD2Vertex* v2 = frame2->vertices + triangle->vertices[j];
            Vec3f pos = v1->pos * (1 - frac) + v2->pos * frac;
            Vec3f normal = v1->normal * (1 - frac) + v2->normal * frac;
            if (normal[0] == 0 && normal[1] == 0 && normal[2] == 0) {
                normal = Vec3f(0, 0, 1);
            }
            

            normals.push_back(normal[0]);
            normals.push_back(normal[1]);
            normals.push_back(normal[2]);

            MD2TexCoord* texCoord = texCoords + triangle->texCoords[j];
            textCoords.push_back(texCoord->texCoordX);
            textCoords.push_back(texCoord->texCoordY);

            vertices.push_back(pos[0]);
            vertices.push_back(pos[1]);
            vertices.push_back(pos[2]);
        }

    }


    glEnableClientState(GL_NORMAL_ARRAY);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);
    glEnableClientState(GL_VERTEX_ARRAY);

    glNormalPointer(GL_FLOAT, 0, &normals[0]);
    glTexCoordPointer(2, GL_FLOAT, 0, &textCoords[0]); 
    glVertexPointer(3, GL_FLOAT, 0, &vertices[0]);



    glDrawArrays(GL_TRIANGLES, 0, vertices.size()/3);

                                    
    glDisableClientState(GL_VERTEX_ARRAY);  // disable vertex arrays
    glDisableClientState(GL_TEXTURE_COORD_ARRAY);
    glDisableClientState(GL_NORMAL_ARRAY);

    vertices.clear();
    textCoords.clear();
    normals.clear();

Is there something extra that I am doing here? Cos this is really meant to be more efficient that glBegin()/End(), right?

Thanks for your time and help!

added 26 characters in body
Source Link
Alex
Alex
  • 103
  • 3

Thanks for yourany help you may be able to provide!

Thanks for your help!

Thanks for any help you may be able to provide!

Source Link
Alex
Alex
  • 103
  • 3

Refactoring an immediate drawing function into VBO, access violation error

I have a MD2 model loader, I am trying to substitute its immediate drawing function with a Vertex Buffer Object one....

I am getting a really annoying access violation reading error and I can't figure out why, but mostly I'd like an opinion as to whether this looks correct (never used VBOs before).

This is the original function (that compiles ok) which calculates the keyframe and draws at the same time:

glBegin(GL_TRIANGLES);
    for(int i = 0; i < numTriangles; i++) {
        MD2Triangle* triangle = triangles + i;
        for(int j = 0; j < 3; j++) {
            MD2Vertex* v1 = frame1->vertices + triangle->vertices[j];
            MD2Vertex* v2 = frame2->vertices + triangle->vertices[j];
            Vec3f pos = v1->pos * (1 - frac) + v2->pos * frac;
            Vec3f normal = v1->normal * (1 - frac) + v2->normal * frac;
            if (normal[0] == 0 && normal[1] == 0 && normal[2] == 0) {
                normal = Vec3f(0, 0, 1);
            }
            glNormal3f(normal[0], normal[1], normal[2]);
            
            MD2TexCoord* texCoord = texCoords + triangle->texCoords[j];
            glTexCoord2f(texCoord->texCoordX, texCoord->texCoordY);
            glVertex3f(pos[0], pos[1], pos[2]);
        }
    }
glEnd();

What I'd like to do is to calculate all positions before hand, store them in a Vertex array and then draw them. This is what I am trying to replace it with (in the exact same part of the program)

int vCount = 0;
    for(int i = 0; i < numTriangles; i++) {
        MD2Triangle* triangle = triangles + i;
        for(int j = 0; j < 3; j++) {
            MD2Vertex* v1 = frame1->vertices + triangle->vertices[j];
            MD2Vertex* v2 = frame2->vertices + triangle->vertices[j];
            Vec3f pos = v1->pos * (1 - frac) + v2->pos * frac;
            Vec3f normal = v1->normal * (1 - frac) + v2->normal * frac;
            if (normal[0] == 0 && normal[1] == 0 && normal[2] == 0) {
                normal = Vec3f(0, 0, 1);
            }
            
            indices[vCount] = normal[0];
            vCount++;
            indices[vCount] = normal[1];
            vCount++;
            indices[vCount] = normal[2];
            vCount++;
            
            MD2TexCoord* texCoord = texCoords + triangle->texCoords[j];
            indices[vCount] = texCoord->texCoordX;
            vCount++;
            indices[vCount] = texCoord->texCoordY;
            vCount++;

            indices[vCount] = pos[0];
            vCount++;
            indices[vCount] = pos[1];
            vCount++;
            indices[vCount] = pos[2];
            vCount++;
        }

    }

         totalVertices = vCount;
        
        glEnableClientState(GL_NORMAL_ARRAY);
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);
    glEnableClientState(GL_VERTEX_ARRAY);


    glNormalPointer(GL_FLOAT, 0, indices);
    glTexCoordPointer(2, GL_FLOAT, sizeof(float)*3, indices);
    glVertexPointer(3, GL_FLOAT, sizeof(float)*5, indices);


    glDrawElements(GL_TRIANGLES, totalVertices, GL_UNSIGNED_BYTE, indices);

    glDisableClientState(GL_VERTEX_ARRAY);  // disable vertex arrays
    glEnableClientState(GL_TEXTURE_COORD_ARRAY);
    glDisableClientState(GL_NORMAL_ARRAY);

First of all, does it look right?

Second, I get access violation error "Unhandled exception at 0x01455626 in Graphics_template_1.exe: 0xC0000005: Access violation reading location 0xed5243c0" pointing at line 7

Vec3f pos = v1->pos * (1 - frac) + v2->pos * frac;

where the two Vs seems to have no value in the debugger.... Till this point the function behaves in exactly the same way as the one above, I don't understand why this happens?

Thanks for your help!