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Shader compiles but vertices not drawn to window

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Shader compiles but vertices not drawn to window
« on: July 08, 2018, 20:04:26 »
I'm new to OpenGL programming so right now I'm just trying to get a simple shader to display a 2-dimensional red triangle. Using various tutorials I've pieced together a program that I think should work but there seems to be a problem with the shader. When I comment out the glUseProgram line I see a white triangle where it's supposed to be according to the obj file vertices. However, when I put the glUseProgram line back in the code compiles successfully but all I get is a black screen. I've attached the shader files. Below is the render method and methods I use to separately load the shaders and compile them into a program.

Code: [Select]
private int loadShader(String shaderFile, int type) {
// read the shader file
ByteBuffer source;
try {
FileInputStream fis = new FileInputStream(shaderFile);
FileChannel fc = fis.getChannel();
source = fc.map(FileChannel.MapMode.READ_ONLY, 0, fc.size());
fc.close();
fis.close();
} catch(FileNotFoundException ex) {
throw new AssertionError("Could not find file \"" + shaderFile + "\"");
} catch(IOException ex) {
throw new AssertionError("Error reading file \"" + shaderFile + "\"");
}

// compile the shader
int shader = glCreateShader(type);
PointerBuffer strings = BufferUtils.createPointerBuffer(1);
IntBuffer lengths = BufferUtils.createIntBuffer(1);
strings.put(0, source);
lengths.put(0, source.remaining());

// check the shader
glShaderSource(shader, strings, lengths);
glCompileShader(shader);
int compiled = glGetShaderi(shader, GL_COMPILE_STATUS);
String shaderLog = glGetShaderInfoLog(shader);
if (shaderLog != null && shaderLog.trim().length() > 0) {
System.err.println(shaderLog);
}
if (compiled == 0) {
throw new AssertionError("Could not compile shader");
}
return shader;
}

public void init() {
// normal glfw init and vertices loaded here but that's cut out because I know that works

// creating the program
String vertexShaderFile = "res/spaceship.vs";
int vertexShader = loadShader(vertexShaderFile, GL_VERTEX_SHADER);
String fragmentShaderFile = "res/spaceship.fs";
int fragmentShader = loadShader(fragmentShaderFile, GL_FRAGMENT_SHADER);

// compile the program
int program = glCreateProgram();
glAttachShader(program, vertexShader);
glAttachShader(program, fragmentShader);
glLinkProgram(program);

// check the program
int linked = glGetProgrami(program, GL_LINK_STATUS);
String programLog = glGetProgramInfoLog(program);
if(programLog != null && programLog.trim().length() > 0) {
System.err.println(programLog);
}
if(linked == 0) {
throw new AssertionError("Could not link program");
}

// this is a member variable
programId = program;

        // Set the clear color
        glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

}

public void render() {
glfwPollEvents();

glViewport(0, 0, fbWidth, fbHeight);

glClear(GL_COLOR_BUFFER_BIT);

// trying to display in 2D
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, width, height, 0, -1, 1);

// "programId" member variable
int program = programId;

// use shader
glUseProgram(program);

// vertex pos attribute buffer
glEnableVertexAttribArray(0);
// "vertices" is a member variable that I know works when glUseProgram(program) is commented out
glBindBuffer(GL_ARRAY_BUFFER, vertices);
glVertexAttribPointer(
0,          // index
2,           // size
GL_FLOAT,         // type
false,  // normalized?
0,          // stride
0          // offset
);

// This DOESN'T work and displays nothing on the screen unless the program is cleared
glDrawArrays(GL_TRIANGLES, 0, numVertices);

// free attrib arrays and clear program
glDisableVertexAttribArray(0);
glUseProgram(0);

// Since the program is cleared this DOES WORK and displays a white triangle at the specified coordinates
glBegin(GL_TRIANGLES);
glVertex2f(10, 10);
glVertex2f(10, 100);
glVertex2f(100, 10);
glEnd();

// swap screen buffers
glfwSwapBuffers(window);
}

And here are the simple shader files.

vertex shader:
spaceship.vs
Code: [Select]
#version 330

layout(location = 0) in vec2 vertexPosition_modelspace;

void main() {
  gl_Position = vec4(vertexPosition_modelspace, 0.0, 1.0);
}

fragment shader:
spaceship.fs
Code: [Select]
#version 330

out vec3 color;

void main() {
  color = vec3(1,0,0);
}
« Last Edit: July 09, 2018, 00:05:59 by smithy545 »