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Simple Interleaved VBO Example

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Simple Interleaved VBO Example
« on: March 14, 2012, 01:29:33 »
I looked around for a simple example that showed how to use interleaved VBOs with LWJGL and came up empty handed.  I found the VBO documentation on the LWJGL site somewhat lacking, especially since it did not give a fully working example.  So, I worked up a simple interleaved VBO example that draws a simple rotating cube on the screen.  On my laptop I was able to get about 1,700 FPS.

The example, including source code, is here:

http://tgustafson.com/2012/03/a-simple-lwjgl-interleaved-vbo-example/

I'd love to get any useful feedback that anyone may have, especially things like "hey, you're doing this wrong", so that I can update the example and make it correct so that other might find it more useful.

*

Offline TJ

  • *
  • 1
Re: Simple Interleaved VBO Example
« Reply #1 on: March 18, 2012, 16:37:06 »
Hi TimmerCA,

Thanks for sharing your code. Since you explicitly asked for feedback, I have had a quick look at your code, and noticed that you use deprecated functionality like: "glEnableClientState", and "glLight". (But perhaps this is not "wrong" per se, just mentioning it).

Recently I have been struggling myself with setting up GLSL shaders in combination with interleaved vertex buffer objects. What I was trying to do, is implement the following code in LWJGL:

http://openglbook.com/the-book/chapter-3-index-buffer-objects-and-primitive-types/

What is great about this code, is that it avoids all deprecated functionality from pre OpenGL 3.1. So, if you learn how to render objects with the techniques presented there, your code will more easily be supported in future OpenGL.

Fortunately, I have been able to implement the above code in LWJGL  :D

Administrators, if you are listening  :), I would really like this example to appear on the WIKI, because the techniques presented therein are very relevant for learning current OpenGL and because these techniques are nontrivial. Here is the code:

Code: [Select]
package test;

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.nio.FloatBuffer;
import java.nio.IntBuffer;
import org.lwjgl.BufferUtils;
import static org.lwjgl.opengl.GL11.*;
import static org.lwjgl.opengl.GL15.*;
import static org.lwjgl.opengl.GL20.*;
import static org.lwjgl.opengl.GL30.*;

import org.lwjgl.LWJGLException;
import org.lwjgl.input.Keyboard;
import org.lwjgl.input.Mouse;
import org.lwjgl.opengl.Display;
import org.lwjgl.opengl.DisplayMode;
import org.lwjgl.opengl.Util;

/**
 * @author TJ
 *
 * This code is an LWJGL implementation of the following C-tutorial, that shows
 * how to render objects with OpenGL 4.0 (and 3.1):
 *
 * http://openglbook.com/the-book/chapter-3-index-buffer-objects-and-primitive-types/
 *
 * If you want to render objects in a non-deprecated way, then this code
 * might be very useful to you, because it shows how to set up shaders,
 * how to set up buffer objects, vertex arrays, how to link buffers to the shader,
 * etc.
 */
public class ShaderTest {

    public static final int DISPLAY_HEIGHT = 600; // window width
    public static final int DISPLAY_WIDTH = 600; // window height

    public static final int POSITION_INDEX = 0; // index of vertex attribute "in_Position"
    public static final int COLOR_INDEX = 1; // index of vertex attribute "in_Color"

    public static final int FLOAT_NUM_BYTES; // sizeof(float) in bytes
    public static final int INT_NUM_BYTES; // sizeof(int) in bytes
    public static final int VEC4_BYTES; // sizeof(vec4) in bytes

    static {
        FLOAT_NUM_BYTES = Float.SIZE / Byte.SIZE;
        INT_NUM_BYTES = Integer.SIZE / Byte.SIZE;
        VEC4_BYTES = 4 * FLOAT_NUM_BYTES;
    }

    // We will create the following OpenGL objects in the code below:
    int VertexShaderId,
            FragmentShaderId,
            ProgramId,
            VaoId,
            VboId,
            IndexBufferId;

    public ShaderTest() {
    }

    public void create() throws LWJGLException, Exception {

        DisplayMode d = new DisplayMode(DISPLAY_WIDTH, DISPLAY_HEIGHT);
        Display.setDisplayMode(d);
        Display.setFullscreen(false);
        Display.setTitle("Shaders and buffers in LWJGL");
        Display.create();

        //Keyboard
        Keyboard.create();

        //Mouse
        Mouse.setGrabbed(false);
        Mouse.create();

        //OpenGL
        initGL();
        resizeGL();
    }

    void Cleanup() {
        DestroyShaders();
        DestroyVBO();
    }

    void CreateVBO() {

        // Create a "vertex array" object.
        // This OpenGL-object will group the "in_Position" and "in_Color"
        // vertex attributes.

        VaoId = glGenVertexArrays();
        Util.checkGLError();

        glBindVertexArray(VaoId);
        Util.checkGLError();

        //==============================================================
        // Next we create the vertex position and color data that we
        // will pass to the shaders.
        // In the array below, we interleave the position and color data:
        // first vec4 for position, then vec4 for color, vec4 for position, etc.

        float[] VerticesArray = new float[]{
            0.0f, 0.0f, 0.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f,
            // Top
            -0.2f, 0.8f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, 1.0f,
            0.2f, 0.8f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f,
            0.0f, 0.8f, 0.0f, 1.0f, 0.0f, 1.0f, 1.0f, 1.0f,
            0.0f, 1.0f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f,
            // Bottom
            -0.2f, -0.8f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f,
            0.2f, -0.8f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, 1.0f,
            0.0f, -0.8f, 0.0f, 1.0f, 0.0f, 1.0f, 1.0f, 1.0f,
            0.0f, -1.0f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f,
            // Left
            -0.8f, -0.2f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, 1.0f,
            -0.8f, 0.2f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f,
            -0.8f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 1.0f, 1.0f,
            -1.0f, 0.0f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f,
            // Right
            0.8f, -0.2f, 0.0f, 1.0f, 0.0f, 0.0f, 1.0f, 1.0f,
            0.8f, 0.2f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, 1.0f,
            0.8f, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 1.0f, 1.0f,
            1.0f, 0.0f, 0.0f, 1.0f, 1.0f, 0.0f, 0.0f, 1.0f
        };

        // Now we put this data in a FloatBuffer, that will be passed to LWJGL.
        // Importantly: use the class BufferUtils, because then your FloatBuffer
        // will be "direct" AND the byte ordering will be native (=required).
        // Using native byte ordering is something that you might easily forget!

        FloatBuffer Vertices = BufferUtils.createFloatBuffer(VerticesArray.length);
        Vertices.put(VerticesArray);
        Vertices.rewind(); // rewind, otherwise LWJGL thinks our buffer is empty

        // We now create a new OpenGL object: a "buffer object" to hold all
        // vertex data from above.
        // We bind the new object to the target "GL_ARRAY_BUFFER" so that we can
        // transfer our above data to OpenGL.
        {
            VboId = glGenBuffers();
            Util.checkGLError();

            glBindBuffer(GL_ARRAY_BUFFER, VboId);
            Util.checkGLError();

            // Transfer all data to the OpenGL-object, saying that it will
            // be used for "static drawing", meaning we will not modify
            // our vertex data in the future (so OpenGL can do optimizations).
            glBufferData(GL_ARRAY_BUFFER, Vertices, GL_STATIC_DRAW);
            Util.checkGLError();
        }

        //==============================================================
        // Now we do something similar as above, but now for the indices,
        // and we use the OpenGL target GL_ELEMENT_ARRAY_BUFFER instead
        // of GL_ARRAY_BUFFER.

        int IndicesArray[] = {
            // Top
            0, 1, 3,
            0, 3, 2,
            3, 1, 4,
            3, 4, 2,
            // Bottom
            0, 5, 7,
            0, 7, 6,
            7, 5, 8,
            7, 8, 6,
            // Left
            0, 9, 11,
            0, 11, 10,
            11, 9, 12,
            11, 12, 10,
            // Right
            0, 13, 15,
            0, 15, 14,
            15, 13, 16,
            15, 16, 14
        };

        IntBuffer Indices = BufferUtils.createIntBuffer(IndicesArray.length);
        Indices.put(IndicesArray);
        Indices.rewind();

        IndexBufferId = glGenBuffers();
        Util.checkGLError();

        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, IndexBufferId);
        Util.checkGLError();

        glBufferData(GL_ELEMENT_ARRAY_BUFFER, Indices, GL_STATIC_DRAW);
        Util.checkGLError();

        //==============================================================      
        // Now we tell OpenGL that we will use POSITION_INDEX and COLOR_INDEX
        // to communicate respectively the vertex positions and vertex colors
        // to our shaders.
        {
            // First we enable the indices. This will affect the vertex
            // array object from above.
            glEnableVertexAttribArray(POSITION_INDEX);
            Util.checkGLError();

            glEnableVertexAttribArray(COLOR_INDEX);
            Util.checkGLError();

            // Then we tell OpenGL how it should read the GL_ARRAY_BUFFER
            // (to which we have bound our vertex data, see above).

            // The position data starts at the beginning of the vertex data
            glVertexAttribPointer(POSITION_INDEX, 4, GL_FLOAT, false,
                    2 * VEC4_BYTES, 0);
            Util.checkGLError();

            // The color data starts after the first 4 floats of position data
            glVertexAttribPointer(COLOR_INDEX, 4, GL_FLOAT, false,
                    2 * VEC4_BYTES, VEC4_BYTES);
            Util.checkGLError();
        }

        // Just to be VERY clean, we will unbind the vertex attribute object
        // and only bind it when we render. This way we cannot accidentally modify
        // it anymore.
        glBindVertexArray(0);
        Util.checkGLError();

        // Only after the vertex array is disabled, we unbind the buffers
        // to the GL_ARRAY_BUFFER and GL_ELEMENT_ARRAY_BUFFER targets, because
        // otherwise the vertex array object would become invalid again.
        glBindBuffer(GL_ARRAY_BUFFER, 0);
        Util.checkGLError();

        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
        Util.checkGLError();
    }

    void DestroyVBO() {

        glDisableVertexAttribArray(POSITION_INDEX);
        Util.checkGLError();

        glDisableVertexAttribArray(COLOR_INDEX);
        Util.checkGLError();

        glBindBuffer(GL_ARRAY_BUFFER, 0);
        Util.checkGLError();

        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
        Util.checkGLError();

        glDeleteBuffers(IndexBufferId);
        Util.checkGLError();

        glDeleteBuffers(VboId);
        Util.checkGLError();

        glBindVertexArray(0);
        Util.checkGLError();

        glDeleteVertexArrays(VaoId);
        Util.checkGLError();
    }

    void CreateShaders() throws IOException {

        // Put the shaders "chap2.vert" and "chap2.frag" in the working
        // directory ...

        //==========================================================
        // Load and compile vertex shader

        String VertexShader = readShaderSourceCode("chap2.vert");

        VertexShaderId = glCreateShader(GL_VERTEX_SHADER);
        Util.checkGLError();

        glShaderSource(VertexShaderId, VertexShader);
        Util.checkGLError();

        glCompileShader(VertexShaderId);
        Util.checkGLError();

        // Print possible compile errors
        System.out.println("Vertex shader compilation:");
        printShaderLog(VertexShaderId);
        Util.checkGLError();

        //==========================================================
        // Load and compile fragment shader

        String FragmentShader = readShaderSourceCode("chap2.frag");

        FragmentShaderId = glCreateShader(GL_FRAGMENT_SHADER);
        Util.checkGLError();

        glShaderSource(FragmentShaderId, FragmentShader);
        Util.checkGLError();

        glCompileShader(FragmentShaderId);
        Util.checkGLError();

        // Print possible compile errors
        System.out.println("Fragment shader compilation:");
        printShaderLog(FragmentShaderId);

        //==========================================================
        // Link shader program

        ProgramId = glCreateProgram();
        Util.checkGLError();

        // Attach vertex shader
        glAttachShader(ProgramId, VertexShaderId);
        Util.checkGLError();

        // Attach fragment shader
        glAttachShader(ProgramId, FragmentShaderId);
        Util.checkGLError();

        // We tell the program how the vertex attribute indices will map
        // to named "in" variables in the vertex shader. This must be done
        // before compiling.
        glBindAttribLocation(ProgramId, POSITION_INDEX, "in_Position");
        glBindAttribLocation(ProgramId, COLOR_INDEX, "in_Color");

        glLinkProgram(ProgramId);
        Util.checkGLError();

        // Print possible compile errors
        System.out.println("Program linking:");
        printProgramLog(ProgramId);

        Util.checkGLError();
        glUseProgram(ProgramId);
        Util.checkGLError();

        Util.checkGLError();
    }

    /**
     * Read shader source code from a file.
     * @param file
     * @return
     * @throws IOException
     */
    public static String readShaderSourceCode(String file) throws IOException {
        String code = "";
        String line;

        BufferedReader reader = new BufferedReader(new FileReader(file));
        while ((line = reader.readLine()) != null) {
            code += line + "\n";
        }

        return code;
    }

    /**
     * Print log of shader object.
     *
     * @param id
     */
    public static void printShaderLog(int id) {
        int logLength = glGetShader(id, GL_INFO_LOG_LENGTH);
        Util.checkGLError();

        System.out.println("  Log (length " + logLength + " chars)");
        String log = glGetShaderInfoLog(id, logLength);
        Util.checkGLError();
        for (String line : log.split("\n")) {
            System.out.println("  " + line);
        }
        System.out.println("");
    }

    /**
     * Print log of program object
     *
     * @param programId
     */
    public static void printProgramLog(int programId) {
        int logLength = glGetProgram(programId, GL_INFO_LOG_LENGTH);
        Util.checkGLError();

        System.out.println("  Log (length " + logLength + " chars)");
        String log = glGetProgramInfoLog(programId, logLength);
        Util.checkGLError();
        for (String line : log.split("\n")) {
            System.out.println("  " + line);
        }
        System.out.println("");
    }

    void DestroyShaders() {

        glUseProgram(0);

        glDetachShader(ProgramId, VertexShaderId);
        glDetachShader(ProgramId, FragmentShaderId);

        glDeleteShader(FragmentShaderId);
        glDeleteShader(VertexShaderId);

        glDeleteProgram(ProgramId);

        Util.checkGLError();
    }

    public void destroy() {
        Cleanup();
        Mouse.destroy();
        Keyboard.destroy();
        Display.destroy();
    }

    public void initGL() throws IOException {

        glClearColor(0, 0, 0, 0);
        glDisable(GL_DEPTH_TEST);
        glDisable(GL_LIGHTING);

        CreateShaders();
        CreateVBO();
    }

    public void processKeyboard() {
    }

    public void processMouse() {
    }

    public void render() throws LWJGLException {
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        Util.checkGLError();

        // Use the vertex array object. This will automatically cause OpenGL
        // to read our vertex position/color data and the indices data.
        glBindVertexArray(VaoId);

        // The glDrawElements function will the vertex attribute object
        // that we have bound.
        glDrawElements(
                GL_TRIANGLES,
                48, // = use all 48 indices from the indices buffer
                GL_UNSIGNED_INT,
                0);
        Util.checkGLError();
    }

    public void resizeGL() {
        glViewport(0, 0, DISPLAY_WIDTH, DISPLAY_HEIGHT);
    }

    public void run() throws LWJGLException {
        while (!Display.isCloseRequested() && !Keyboard.isKeyDown(Keyboard.KEY_ESCAPE)) {
            if (Display.isVisible()) {
                processKeyboard();
                processMouse();
                update();
                render();
            } else {
                if (Display.isDirty()) {
                    render();
                }
                try {
                    Thread.sleep(100);
                } catch (InterruptedException ex) {
                }
            }

            Display.update();
            Display.sync(60);
        }
    }

    public void update() {
    }

    public static void main(String[] args) {
        ShaderTest main = null;
        try {
            main = new ShaderTest();
            main.create();
            main.run();
        } catch (Exception ex) {
            ex.printStackTrace();
        } finally {
            if (main != null) {
                main.destroy();
            }
        }
    }
}


Here is the vertex shader (file "chap2.vert"):
Code: [Select]
#version 140
 
in vec4 in_Position;
in vec4 in_Color;
out vec4 ex_Color;
 
void main(void)
{
   gl_Position = in_Position;
   ex_Color = in_Color;
}

Here is the fragment shader ("chap2.frag"):
Code: [Select]
#version 140
 
in vec4 ex_Color;
out vec4 out_Color;
   
void main(void)
{
   out_Color = ex_Color;
}
« Last Edit: March 18, 2012, 16:42:12 by TJ »