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POVBO dissapearing, bad Matrix?
 

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  1. POVBO dissapearing, bad Matrix?
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    <p>I'm not sure why but my VBO is disappearing after one frame (initial frame shows it at the origin improperly angled) Below is the code for my matrix class, the draw method, and the vertex shader.</p> <pre><code>Matrix::Matrix() { for (int i = 0; i &lt; 16; i++) { values[i] = 0; } } Matrix Matrix::operator*(const Matrix &amp;matrix) { Matrix result; for (int i = 0; i &lt; 4; i++) { for (int j = 0; j &lt; 4; j++) { for (int k = 0; k &lt; 4; k++) { result.values[i * 4 + j] += this-&gt;values[i * 4 + k] * matrix.values[k * 4 + j]; } } } return result; } Matrix Matrix::Perspective(float fov, float aspect, float znear, float zfar) { Matrix matrix; float xymax = znear * tan(fov * 0.00872664); float q = -(zfar * znear) / (zfar - znear); float val = znear / xymax; matrix.values[0] = val / aspect; matrix.values[5] = val; matrix.values[10] = q; matrix.values[11] = -1; matrix.values[14] = 2 * q; return matrix; } Matrix Matrix::LookAt(Vector3f eye, Vector3f target, Vector3f up) { Vector3f zaxis = Vector3f::Normalize(target - eye); Vector3f xaxis = Vector3f::Normalize(Vector3f::CrossProduct(up, zaxis)); Vector3f yaxis = Vector3f::CrossProduct(zaxis, xaxis); // vy doesn't need to be normalized because it's a cross product of 2 normalized vectors Matrix viewMatrix; viewMatrix.values[0] = xaxis.x; viewMatrix.values[1] = xaxis.y; viewMatrix.values[2] = xaxis.z; viewMatrix.values[3] = 0; viewMatrix.values[4] = yaxis.x; viewMatrix.values[5] = yaxis.y; viewMatrix.values[6] = yaxis.z; viewMatrix.values[7] = 0; viewMatrix.values[8] = zaxis.x; viewMatrix.values[9] = zaxis.y; viewMatrix.values[10] = zaxis.z; viewMatrix.values[11] = 0; viewMatrix.values[12] = 0; viewMatrix.values[13] = 0; viewMatrix.values[14] = 0; viewMatrix.values[15] = 1; Matrix translationMatrix = Matrix::Identity(); translationMatrix.values[12] = -eye.x; translationMatrix.values[13] = -eye.y; translationMatrix.values[14] = -eye.z; return translationMatrix * viewMatrix; } Matrix Matrix::Identity() { Matrix matrix; matrix.values[0] = 1; matrix.values[5] = 1; matrix.values[10] = 1; matrix.values[15] = 1; return matrix; } </code></pre> <p>Variables:</p> <pre><code>static const GLfloat g_vertex_buffer_data[] = { -1.0f, -1.0f, 0.0f, 1.0f, -1.0f, 0.0f, 0.0f, 1.0f, 0.0f }; GLuint vertexbuffer; GLuint programID; </code></pre> <p>Draw method:</p> <pre><code>void draw() { glClearColor(0.5, 0.5, 0.5, 1.0); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT); glUseProgram(programID); Matrix projection = Matrix::Perspective(45.0f, (float)(screen_size.x) / screen_size.y, 0.1f, 1000.0f); Matrix view = Matrix::LookAt(Vector3f(4, 3, 3), Vector3f(0, 0, 0), Vector3f(0, 1, 0)); Matrix model = Matrix::Identity(); Matrix mvp = projection * view * model; GLuint matrixID = glGetUniformLocation(programID, "mvp"); glUniformMatrix4fv(matrixID, 1, GL_FALSE, mvp.values); int positionId = glGetAttribLocation(programID, "position"); glEnableVertexAttribArray(positionId); glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer); glVertexAttribPointer(positionId, 3, GL_FLOAT, GL_FALSE, 0, (void *)0); glDrawArrays(GL_TRIANGLES, 0, 3); glDisableVertexAttribArray(positionId); glutSwapBuffers(); } </code></pre> <p>Vertex Shader:</p> <pre><code>in vec3 position; uniform mat4 mvp; void main() { gl_Position = mvp * vec4(position, 1); } </code></pre>
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    1. PTQuestion
    1. USBenjamin Danger Johnson
    1. USBenjamin Danger Johnson
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      1. POVBO dissapearing, bad Matrix?
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      1. VTUpMod
    1. COHave you tried unrolling your matrix multiplication loop? To be honest, I would not even try to tell if it is doing the right thing...
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      1. POVBO dissapearing, bad Matrix?
      1. UScli_hlt
    2. COwhat do you mean unroll my matrix multiplication loop? I've tried passing just the identity matrix and that works fine (get a nice big fat triangle on my screen.) Honestly I feel like i must have done a matrix function wrong, but I copied the code from a bunch of other people asking how to preform the above operations.
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      1. POVBO dissapearing, bad Matrix?
      1. USBenjamin Danger Johnson
    3. COWell I've done a bunch of matrix multiplication implementations and I've also seen a lot, but I have never encountered a loop there. Try something like this http://pastebin.com/RD4Cmdqg .
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      1. POVBO dissapearing, bad Matrix?
      1. UScli_hlt
 

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