CG[LWJGL0017] || Shader Dasar

ShaderProgram.java

package latihanShader00;
import java.io.BufferedReader;
import java.io.FileReader;
  
import org.lwjgl.opengl.GL11;
import org.lwjgl.opengl.GL20;
import static org.lwjgl.opengl.GL20.*;
 
// class ini digunakan untuk meload dan mengcompile shader 
 
 
public class ShaderProgram {
        // OpenGL handle yang menunjuk ke executable shader program
        private int programId;
      
        public void init(String vertexShaderFilename, String fragmentShaderFilename){
            // buat shader program. jika berhasil  OK, buat vertex dan fragment shaders
            programId = glCreateProgram();
      
            // load and compile shaders (vertex dan fragment)
            int vertShader = loadAndCompileShader(vertexShaderFilename, GL_VERTEX_SHADER);
            int fragShader = loadAndCompileShader(fragmentShaderFilename, GL_FRAGMENT_SHADER);
      
            // attach shaders yg sudah dikompilasi ke program
            glAttachShader(programId, vertShader);
            glAttachShader(programId, fragShader);
      
            // melakukan link program
            glLinkProgram(programId);
      
            //validasi link shader
            if (glGetProgrami(programId, GL_LINK_STATUS) == GL11.GL_FALSE){
                throw new RuntimeException("tidak dapat melakukan link shader. Reason: " + glGetProgramInfoLog(programId, 1000));
            }
      
            //melakukan validasi shader
            glValidateProgram(programId);
      
            if (glGetProgrami(programId, GL_VALIDATE_STATUS) == GL11.GL_FALSE){
                throw new RuntimeException("Tidak dapat memvalidasi shader. Reason: " + glGetProgramInfoLog(programId, 1000));            
            }
        }
      
       /**
        * With the exception of syntax, setting up vertex and fragment shaders
        * is the same.
        * @param the name and path to the vertex shader
        */
        private int loadAndCompileShader(String filename, int shaderType){
            //vertShader akan bernilai != 0 juka shader berhasil dibuat
            int handle = glCreateShader(shaderType);
      
            if( handle == 0 ){
                throw new RuntimeException("Tidak dapat membuat shader dengan type "+shaderType+" untuk file "+filename+". "+ glGetProgramInfoLog(programId, 1000));
            }
      
            // me-load code dari file menjadi String Shader
            String code = loadFile(filename);
      
            // upload code ke OpenGL dan menggabungkan code dengan shader
            glShaderSource(handle, code);
      
            // meng-compile source code ke binary
            glCompileShader(handle);
      
            // acquire compilation status
            int shaderStatus = glGetShaderi(handle, GL20.GL_COMPILE_STATUS);
      
            //memeriksa apakah proses compile berhasil
            if( shaderStatus == GL11.GL_FALSE){
                throw new IllegalStateException("kesalahan kompilasi shader ["+filename+"]. Info: " + glGetShaderInfoLog(handle, 1000));
            }      
            return handle;
        }
      
        /**
         * me-load sebuah file teks dan me-return String isi file yang berisi script shader.
         */
        private String loadFile(String filename){
            StringBuilder vertexCode = new StringBuilder();
            String line = null ;
            try{
                BufferedReader reader = new BufferedReader(new FileReader(filename));
                while( (line = reader.readLine()) !=null ){
                    vertexCode.append(line);
                    vertexCode.append('\n');
                }
                reader.close();
            }catch(Exception e){
                throw new IllegalArgumentException("gagal me-load shader dari file ["+filename+"]", e);
            }      
            return vertexCode.toString();
        }
      
      
        public int getProgramId(){
            return programId;
        }    
}