3 LAB : Sending Data to Shaders

Sending Data using Outs and Ins (Shader → Shader)

[Code] 1-colored-triangle-outin

Vertex shader

#version 330 core
layout (location = 0) in vec3 vin_pos; 
**out vec4 vout_color;**
void main()
{
		gl_Position = vec4(vin_pos.x, vin_pos.y, vin_pos.z, 1.0);
    vout_color = vec4(0,1,0,1); #rgb에서 g만 1 => green color
}

out vec4 vout_color : output variable을 만들어줌

Fragment shader

#version 330 core
**in vec4 vout_color;** 
out vec4 FragColor; 
void main()
{
    FragColor = vout_color;
}

in vec4 vout_color : 같은 type와 name으로 Input variable 만듦

Sending Data by Specifying Vertex Attributes

(Application → Shader)**

Add More Vertex Attributes

Add per-vertex color:

vertices = glm.array(glm.float32, 
				# position         # color
				-1.0, -1.0, 0.0,   1.0, 0.0, 0.0, # left vertex 
				1.0, -1.0, 0.0,    0.0, 1.0, 0.0, # right vertex 
				0.0, 1.0, 0.0,     0.0, 0.0, 1.0, # top vertex
)

→ vertex별로 position과 color

Change in Vertex Shader

Vertex position: 0
Vertex color: 1

#version 330 core

layout (location = 0) in vec3 vin_pos; 
layout (location = 1) in vec3 vin_color;

out vec4 vout_color;

void main() {
		gl_Position = vec4(vin_pos.x, vin_pos.y, vin_pos.z, 1.0);
		vout_color = vec4(vin_color,1); # you can pass a vec3 and a scalar to vec4 constructor
}

→ position 받는 layout의 location은 0, color 받는 layout의 location은 1로 해줌

fragment shade은 동일

#version 330 core
in vec4 vout_color; 
out vec4 FragColor;

void main() {
		FragColor = vout_color; 
}

Changes in Attributes Configuration

attributes configuration

# configure vertex positions - index 0 
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 
6*glm.sizeof(glm.float32), None) 
glEnableVertexAttribArray(0)

# configure vertex colors - index 1
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 
6*glm.sizeof(glm.float32), 
ctypes.c_void_p(3*glm.sizeof(glm.float32))) 
glEnableVertexAttribArray(1)