Basic Rendering from VBOs with Shaders

[DylanP1234]

Hey guys,

I think I have a problem... Well possibly I am just too dumb to understand OpenGL but anyways...

As the title says, I am just trying to put some simple data (a quad) into a VBO and then render it with a vertexshader and a fragmentshader.

So this is the vertexshader code:

#version 450

attribute vec3 position;
attribute vec4 color;

out vec4 pass_color;

void main()
{
	pass_color = color;
	
	gl_Position = vec4(position, 1.0);
}

And that's the fragmentshader code:

#version 450

in vec4 pass_color;

void main()
{
	gl_FragColor = pass_color;
}

So they are very basic - nothing special. Just always set the position to the position coming from the attribute and always set the color to the color coming from the attribute.

First, I am going to show you my "data" which are 2 float arrays with some position data and color data:

public static float[] plane_vertices =
		{
				-0.5f, -0.5f, 0f,
				-0.5f, 0.5f, 0f,
				0.5f, 0.5f, 0f,
				
				0.5f, 0.5f, 0f,
				0.5f, -0.5f, 0f,
				-0.5f, -0.5f, 0f
		};
	
	public static float[] plane_colors =
		{
				1.0f, 1.0f, 1.0f, 1.0f,
				0.5f, 0.5f, 0.5f, 1.0f,
				0.0f, 0.0f, 0.0f, 1.0f,
				
				1.0f, 0.0f, 0.0f, 1.0f,
				0.6f, 0.0f, 0.0f, 1.0f,
				0.3f, 0.0f, 0.0f, 1.0f
		};

Yes, I know they should be called "quad" instead of "plane" because they are representing a quad and not a 3D-plane but just bare with me there.

I am using this data to put them into FloatBuffers like this:

// Just generate some Floatbuffers
		
		FloatBuffer plane_verts = BufferUtils.createFloatBuffer(_Const.plane_vertices.length);
		plane_verts.put(_Const.plane_vertices);
		plane_verts.flip();
		
		FloatBuffer plane_cols = BufferUtils.createFloatBuffer(_Const.plane_colors.length);
		plane_cols.put(_Const.plane_colors);
		plane_cols.flip();

That's still nothing special isn't it?

Now we are getting to the interesting parts...

I am setting up the shaders and a shaderprogram. Also I am creating a VAO and two VBOs which shall represent my position and color buffers.

vertexShader = new Shader(GL_VERTEX_SHADER, TextLoader.fileToString(_Const.RES_SHADERS + "minimalist_vertexShader.glsl"));
		fragmentShader = new Shader(GL_FRAGMENT_SHADER, TextLoader.fileToString(_Const.RES_SHADERS + "minimalist_fragmentShader.glsl"));
		testShaderProgram = new TestShaderProgram(vertexShader, fragmentShader);
		testShaderProgram.compile();
		
		vao = new VAO();
		
		vao.bind();
		
		vbo_position = new VBO();
		vbo_color = new VBO();

After that I am using the following code to "upload" the data into the VBOs:

// Upload the data into the vbos
		
		vbo_position.bind(GL_ARRAY_BUFFER);
		glBufferData(GL_ARRAY_BUFFER, plane_verts, GL_STATIC_DRAW);
		glVertexAttribPointer(0, 3, GL_FLOAT, false, 0, plane_verts);
		VBO.unbind(GL_ARRAY_BUFFER);
		
		vbo_color.bind(GL_ARRAY_BUFFER);
		glBufferData(GL_ARRAY_BUFFER, plane_cols, GL_STATIC_DRAW);
		glVertexAttribPointer(1, 4, GL_FLOAT, false, 0, plane_cols);
		VBO.unbind(GL_ARRAY_BUFFER);
		
		VAO.unbind();

Please tell me if I have done something wrong here already^^. I hope that It's correct though. Just set the position-data to the first attribute and the color-data to the second. (I am connecting the variable-name in the shader and attribute-location in the testShaderProgram.compile() which we had after creating the shaderprogram.

And this is the code I use to render everything:

public void render()
	{
		clear();
		
		// RENDER HERE
		
		testShaderProgram.use();
		
		vao.bind();
		glEnableVertexAttribArray(0);
		glEnableVertexAttribArray(1);
		
		glDrawArrays(GL_TRIANGLES, 0, 6);
		
		glDisableVertexAttribArray(0);
		glDisableVertexAttribArray(1);
		VAO.unbind();
		
		ShaderProgram.stopUse();
		
		// RENDER END
		
		glfwSwapBuffers(window);
		glfwPollEvents();
	}

So again:
"teshShaderProgram.use();" just activates my shaderprogram which we have created above.
The vao variable is just the VAO for holding my "quad" as you can see above (plane_vertices, plane_colors).
"vao.bind();" obviously binds that vao.

Unfortunately, everything shows me a black window, which is kinda sad
My guess is that I am a bit confused by all the states and that I have set something wrong at the wrong moment so everything doesn't work.

I really hope some of you guys can help me out with this (I hope super-simple) problem.

P.S.: What's the difference in using glBufferData(with buffer) and then glVertexAttribPointer(without a buffer) and just using glVertexAttribPointer(with a buffer)?

Thanks in advance for your help!

[ErChick3n]

I didn't read all ur code but certainly u have to add an output in ur fragment shader otherwise u won't be able to see anything.

in the end your fragment shader should look more like this:

#version 450
 
in vec4 pass_color;
 
out vec4 gl_FragColor;

void main()
{
    gl_FragColor = pass_color;
}