Hello.
I hava basic qiestion how to display two squares?
Based on this tutorial
http://lwjgl.org/wiki/index.php?title=The_Quad_interleaved
I know how to display square even cube but I don’t know how to display two square (or cube).
I was thinking that I need only to set vertices
e.g.
float[] vertices = {
-0.2f, 0.2f, 0f, 1f,
-0.2f, -0.2f, 0f, 1f,
0.2f, -0.2f, 0f, 1f,
0.2f, 0.2f, 0f, 1f,
0.3f, 0.2f, 0f, 1f,
0.3f, -0.2f, 0f, 1f,
0.6f, -0.2f, 0f, 1f,
0.6f, 0.2f, 0f, 1f};
and colors:
float[] colors = {
1f, 0f, 0f, 1f,
0f, 1f, 0f, 1f,
0f, 0f, 1f, 1f,
1f, 1f, 1f, 1f,
1f, 0f, 0f, 1f,
0f, 1f, 0f, 1f,
0f, 0f, 1f, 1f,
1f, 1f, 1f, 1f
};
but it doesn’t work the second square does not appear.
Do I need to do something else with indices array?
How to tell OpenGL that after drawing first square move on this position and draw another square.
Here is my whole code
package com.opengl3.tutorial.frame;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.FloatBuffer;
import org.lwjgl.BufferUtils;
import org.lwjgl.LWJGLException;
import org.lwjgl.opengl.ContextAttribs;
import org.lwjgl.opengl.Display;
import org.lwjgl.opengl.DisplayMode;
import org.lwjgl.opengl.GL11;
import org.lwjgl.opengl.GL15;
import org.lwjgl.opengl.GL20;
import org.lwjgl.opengl.GL30;
import org.lwjgl.opengl.PixelFormat;
import org.lwjgl.util.glu.GLU;
public class TheQuadExampleColored {
// Entry point for the application
public static void main(String[] args) {
new TheQuadExampleColored();
}
// Setup variables
private final String WINDOW_TITLE = "The Quad: colored";
private final int WIDTH = 800;
private final int HEIGHT = 600;
// Quad variables
private int vaoId = 0;
private int vboId = 0;
private int vbocId = 0;
private int vboiId = 0;
private int indicesCount = 0;
// Shader variables
private int vsId = 0;
private int fsId = 0;
private int pId = 0;
public TheQuadExampleColored() {
// Initialize OpenGL (Display)
this.setupOpenGL();
this.setupQuad();
this.setupShaders();
while (!Display.isCloseRequested()) {
// Do a single loop (logic/render)
this.loopCycle();
// Force a maximum FPS of about 60
Display.sync(60);
// Let the CPU synchronize with the GPU if GPU is tagging behind
Display.update();
}
// Destroy OpenGL (Display)
this.destroyOpenGL();
}
public void setupOpenGL() {
// Setup an OpenGL context with API version 3.2
try {
PixelFormat pixelFormat = new PixelFormat();
ContextAttribs contextAtrributes = new ContextAttribs(3, 2);
contextAtrributes.withForwardCompatible(true);
contextAtrributes.withProfileCore(true);
Display.setDisplayMode(new DisplayMode(WIDTH, HEIGHT));
Display.setTitle(WINDOW_TITLE);
Display.create(pixelFormat, contextAtrributes);
GL11.glViewport(0, 0, WIDTH, HEIGHT);
} catch (LWJGLException e) {
e.printStackTrace();
System.exit(-1);
}
// Setup an XNA like background color
GL11.glClearColor(0.4f, 0.6f, 0.9f, 0f);
// Map the internal OpenGL coordinate system to the entire screen
GL11.glViewport(0, 0, WIDTH, HEIGHT);
}
public void setupQuad() {
// Vertices, the order is not important. XYZW instead of XYZ
float[] vertices = {
-0.2f, 0.2f, 0f, 1f,
-0.2f, -0.2f, 0f, 1f,
0.2f, -0.2f, 0f, 1f,
0.2f, 0.2f, 0f, 1f,
0.3f, 0.2f, 0f, 1f,
0.3f, -0.2f, 0f, 1f,
0.6f, -0.2f, 0f, 1f,
0.6f, 0.2f, 0f, 1f};
FloatBuffer verticesBuffer = BufferUtils
.createFloatBuffer(vertices.length);
verticesBuffer.put(vertices);
verticesBuffer.flip();
float[] colors = {
1f, 0f, 0f, 1f,
0f, 1f, 0f, 1f,
0f, 0f, 1f, 1f,
1f, 1f, 1f, 1f,
1f, 0f, 0f, 1f,
0f, 1f, 0f, 1f,
0f, 0f, 1f, 1f,
1f, 1f, 1f, 1f
};
FloatBuffer colorsBuffer = BufferUtils.createFloatBuffer(colors.length);
colorsBuffer.put(colors);
colorsBuffer.flip();
// OpenGL expects to draw vertices in counter clockwise order by default
byte[] indices = {
0, 1, 2,
2, 3, 0,
};
indicesCount = indices.length;
ByteBuffer indicesBuffer = BufferUtils.createByteBuffer(indicesCount);
indicesBuffer.put(indices);
indicesBuffer.flip();
// Create a new Vertex Array Object in memory and select it (bind)
vaoId = GL30.glGenVertexArrays();
GL30.glBindVertexArray(vaoId);
// Create a new Vertex Buffer Object in memory and select it (bind) -
// VERTICES
vboId = GL15.glGenBuffers();
GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER, vboId);
GL15.glBufferData(GL15.GL_ARRAY_BUFFER, colorsBuffer,GL15.GL_STATIC_DRAW);
GL20.glVertexAttribPointer(0, 4, GL11.GL_FLOAT, false, 0, 0);
GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER, 0);
// Create a new VBO for the indices and select it (bind) - COLORS
vbocId = GL15.glGenBuffers();
GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER, vbocId);
GL15.glBufferData(GL15.GL_ARRAY_BUFFER, verticesBuffer,GL15.GL_STATIC_DRAW);
GL20.glVertexAttribPointer(1, 4, GL11.GL_FLOAT, false, 0, 0);
GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER, 0);
// Deselect (bind to 0) the VAO
GL30.glBindVertexArray(0);
// Create a new VBO for the indices and select it (bind) - INDICES
vboiId = GL15.glGenBuffers();
GL15.glBindBuffer(GL15.GL_ELEMENT_ARRAY_BUFFER, vboiId);
GL15.glBufferData(GL15.GL_ELEMENT_ARRAY_BUFFER, indicesBuffer,GL15.GL_STATIC_DRAW);
GL15.glBindBuffer(GL15.GL_ELEMENT_ARRAY_BUFFER, 0);
}
private void setupShaders() {
int errorCheckValue = GL11.glGetError();
// Load the vertex shader
vsId = this.loadShader("src/com/opengl3/tutorial/frame/vertex.glsl", GL20.GL_VERTEX_SHADER);
// Load the fragment shader
fsId = this.loadShader("src/com/opengl3/tutorial/frame/fragment.glsl",GL20.GL_FRAGMENT_SHADER);
// Create a new shader program that links both shaders
pId = GL20.glCreateProgram();
GL20.glAttachShader(pId, vsId);
GL20.glAttachShader(pId, fsId);
GL20.glLinkProgram(pId);
// Position information will be attribute 0
GL20.glBindAttribLocation(pId, 0, "in_Position");
// Color information will be attribute 1
GL20.glBindAttribLocation(pId, 1, "in_Color");
GL20.glValidateProgram(pId);
errorCheckValue = GL11.glGetError();
if (errorCheckValue != GL11.GL_NO_ERROR) {
System.out.println("ERROR - Could not create the shaders:"
+ GLU.gluErrorString(errorCheckValue));
System.exit(-1);
}
}
public void loopCycle() {
GL11.glClear(GL11.GL_COLOR_BUFFER_BIT);
GL20.glUseProgram(pId);
// Bind to the VAO that has all the information about the vertices
GL30.glBindVertexArray(vaoId);
GL20.glEnableVertexAttribArray(0);
GL20.glEnableVertexAttribArray(1);
// Bind to the index VBO that has all the information about the order of
// the vertices
GL15.glBindBuffer(GL15.GL_ELEMENT_ARRAY_BUFFER, vboiId);
// Draw the vertices
GL11.glDrawElements(GL11.GL_TRIANGLES, indicesCount,GL11.GL_UNSIGNED_BYTE, 0);
// Put everything back to default (deselect)
GL15.glBindBuffer(GL15.GL_ELEMENT_ARRAY_BUFFER, 0);
GL20.glDisableVertexAttribArray(0);
GL20.glDisableVertexAttribArray(1);
GL30.glBindVertexArray(0);
GL20.glUseProgram(0);
}
public void destroyOpenGL() {
// Delete the shaders
GL20.glUseProgram(0);
GL20.glDetachShader(pId, vsId);
GL20.glDetachShader(pId, fsId);
GL20.glDeleteShader(vsId);
GL20.glDeleteShader(fsId);
GL20.glDeleteProgram(pId);
// Select the VAO
GL30.glBindVertexArray(vaoId);
// Disable the VBO index from the VAO attributes list
GL20.glDisableVertexAttribArray(0);
GL20.glDisableVertexAttribArray(1);
// Delete the vertex VBO
GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER, 0);
GL15.glDeleteBuffers(vboId);
// Delete the color VBO
GL15.glBindBuffer(GL15.GL_ARRAY_BUFFER, 0);
GL15.glDeleteBuffers(vbocId);
// Delete the index VBO
GL15.glBindBuffer(GL15.GL_ELEMENT_ARRAY_BUFFER, 0);
GL15.glDeleteBuffers(vboiId);
// Delete the VAO
GL30.glBindVertexArray(0);
GL30.glDeleteVertexArrays(vaoId);
Display.destroy();
}
public int loadShader(String filename, int type) {
StringBuilder shaderSource = new StringBuilder();
int shaderID = 0;
try {
BufferedReader reader = new BufferedReader(new FileReader(filename));
String line;
while ((line = reader.readLine()) != null) {
shaderSource.append(line).append("\n");
}
reader.close();
} catch (IOException e) {
System.err.println("Could not read file.");
e.printStackTrace();
System.exit(-1);
}
shaderID = GL20.glCreateShader(type);
GL20.glShaderSource(shaderID, shaderSource);
GL20.glCompileShader(shaderID);
return shaderID;
}
}
/////////////////////////////
#vertex.glsl
in vec4 in_Position;
in vec4 in_Color;
out vec4 pass_Color;
void main(void) {
gl_Position = in_Position;
pass_Color = in_Color;
}
/////////////////////
#fragment.glsl
in vec4 pass_Color;
out vec4 out_Color;
void main(void) {
out_Color = pass_Color;
}