Trident International Graphics Workshop2014 3/5
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The document outlines the third day of a 5-day graphics programming workshop focused on Cocos-2D-x, covering topics such as index buffers, 3D geometry creation, lighting, and shading techniques including Lambert and Phong shading. It includes detailed examples of code for rendering a sphere, applying normal vectors, and utilizing vertex and index arrays to optimize performance. Participants learn to set up a camera class and manage the computational aspects of 3D graphics, culminating in practical exercises to create a sphere mesh.
![ Reduce vertex count and speed up
Using index buffer
- Vertex array only
Glfloat vertices[] = {0, 0, 1, 0, 1, 1, 1, 1, 0, 1, 0, 0};
glDrawArrays(GL_TRIANGLES, 0, 6);
- Vertex array and index array
Glfloat vertices[] = {0, 0, 1, 0, 1, 1, 0, 1};
Glushort indices[] = {0, 1, 2, 2, 3, 0};
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, vertices);
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Trident International Graphics Workshop2014 3/5
- 1. International 5-days Graphics Programming Workshop using Cocos-2d-x DAY 3 Trident College of Information Technology Takao WADA
- 2. 1. Review 2. Index buffer 3. Draw a sphere 4. Lambert shading 5. Phong shading Agenda
- 3. Create a 3-D geometry Depth buffer and depth test Transform a geometry using matrices Camera class Compose 2-D and 3-D Review
- 4. Reduce vertex count and speed up Using index buffer - Vertex array only Glfloat vertices[] = {0, 0, 1, 0, 1, 1, 1, 1, 0, 1, 0, 0}; glDrawArrays(GL_TRIANGLES, 0, 6); - Vertex array and index array Glfloat vertices[] = {0, 0, 1, 0, 1, 1, 0, 1}; Glushort indices[] = {0, 1, 2, 2, 3, 0}; glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_SHORT, vertices); 0 3 2 1
- 5. Normal vector A vector perpendicular to a face Defines how a surface reflects light Light Directional light Light direction Point light Light position Lighting basics
- 6. I = Id * kd * cos = Id * kd * (L N) I : Intensity Id : Diffuse Light color Kd : Diffuse color of material L : Light direction N : Normal vector Lambert’s law N L L N L N N L
- 7. 1. Add normal vector to a vertex format 2. Write a vertex shader program 3. Change the parameter(s) Work 3-2
- 8. I = Is * ks * (R E)n I : Intensity Is : Specular light color ks : Specular color of material R : Reflection vector L : Direction of a light N: Normal vector E : Eye position n : Power of speculation Phong shading N E R L
- 9. I = Is * ks * (H N)n I : Intensity Is : Specular light color ks : Specular color of material L : Direction of a light H : Half vector (L + E) E : Eye position N: Normal vector n : Power of speculation Blinn-Phong shading N E H L
- 10. Creating a sphere mesh Silices Rings float phi = M_PI / 2 - i * M_PI / numRings; y = radius * sinf(phi); rcosphi = radius * cosf(phi); y = r sin r cos r: radius float theta = j * 2 * M_PI / numSlices; x = rcosphi * sinf(theta); z = rcosphi * cosf(theta); I = 2 i = 1 Y i = 3 j = 0 j = 1 j = 2 j = 3 j = 4 j = 5 j = 8 j = 6 j = 7 For each ring For each slice Final vertex is rapped for texturingx = r cos sin z = r cos cos Z X X
- 11. 1. Setup a camera class 2. Create and draw a sphere 1. Copy from DiceShaderNode to SphereShaderNode 2. Replace the word “DiceShaderNode” into “SphereShaderNode” 3. Remove the “s_vertices” variable and data. 4. Add the protected variable “GLfloat *_vertices” to “SphereShaderNode.h” 5. Add statements to “initWithVertex” function to create vertices of a sphere 1. Prepare variables of number of rings and number of slices int numRings = 4; int numSlices = 8; 2. Compute vertex count int numVertices = (numRings – 1) * (numSlices +1) + 2; Work 3-1