opengl_x11

commit 2e3cf4e48f6aec3834e75675b2fd7847beabdc3b
parent 9e27f5e0bb85d094da7b93b84b0190f201fa9c1c
Author: bsandro <email@bsandro.tech>
Date:   Sun, 30 Nov 2025 22:39:10 +0200

squares are colored differently now

Diffstat:
M
obj2d.c
 | 
31
+++++++++++++++++++------------

1 file changed, 19 insertions(+), 12 deletions(-)
diff --git a/obj2d.c b/obj2d.c
@@ -36,8 +36,11 @@ static double t_started;
 static const GLchar *vertexSrc = R"(
 #version 420
 layout(location=0) in vec2 position;
+layout(location=1) in vec3 color;
+out vec3 dotColor;
 void main() {
     gl_Position = vec4(position, 0.0, 1.0);
+    dotColor = color;
 }
 )";
 
@@ -45,7 +48,10 @@ static const GLchar *geometrySrc = R"(
 #version 420
 layout(points) in;
 layout(line_strip,max_vertices=6) out;
+in vec3 dotColor[];
+out vec3 fColor;
 void main() {
+    fColor = dotColor[0];
     vec4 p = gl_in[0].gl_Position;
     gl_Position = p+vec4(-0.1, -0.1, 0.0, 0.0);
     EmitVertex();
@@ -64,13 +70,10 @@ void main() {
 static const GLchar *fragmentSrc = R"(
 #version 420
 uniform double iTime;
+in vec3 fColor;
 out vec4 outColor;
 void main() {
-    vec3 color;
-    color.r = 0.2;
-    color.g = 0.6;
-    color.b = 0.1;
-    outColor = vec4(color, 1.0);
+    outColor = vec4(fColor, 1.0);
 }
 )";
 
@@ -94,6 +97,7 @@ static GLuint linkProgram(GLuint vertex, GLuint geometry, GLuint fragment) {
     glAttachShader(shaderProgram, geometry);
     glAttachShader(shaderProgram, fragment);
     glBindAttribLocation(shaderProgram, 0, "position");
+    glBindAttribLocation(shaderProgram, 1, "color");
     glLinkProgram(shaderProgram);
     return shaderProgram;
 }
@@ -151,12 +155,12 @@ int main(int argc, char *argv[]) {
     glGenVertexArrays(1, &vao);
     glBindVertexArray(vao);
 
-    // x,y
-    static const GLfloat vertices[][2] = {
-        {-0.3, -0.5},
-        { 0.6, -0.1},
-        { 0.4,  0.4},
-        {-0.5,  0.6}
+    // x,y, color(r,g,b)
+    static const GLfloat vertices[][5] = {
+        {-0.3, -0.5, 1.f, 0.f, 0.f},
+        { 0.6, -0.1, 0.f, 1.f, 0.f},
+        { 0.4,  0.4, 0.f, 0.f, 1.f},
+        {-0.5,  0.6, 1.f, 1.f, 0.f}
     };
 
     GLuint vbo;
@@ -174,8 +178,11 @@ int main(int argc, char *argv[]) {
     printf("shader link status: %s\n", prgStatus == GL_TRUE ? "ok" : "error");
 
     GLint position = glGetAttribLocation(shaderPrg, "position");
-    glVertexAttribPointer(position, 2, GL_FLOAT, GL_FALSE, 2*sizeof(GLfloat), (void *)0);
+    glVertexAttribPointer(position, 2, GL_FLOAT, GL_FALSE, 5*sizeof(GLfloat), (void *)0);
     glEnableVertexAttribArray(position);
+    GLint color = glGetAttribLocation(shaderPrg, "color");
+    glVertexAttribPointer(color, 3, GL_FLOAT, GL_FALSE, 5*sizeof(GLfloat), (void*)(2*sizeof(GLfloat)));
+    glEnableVertexAttribArray(color);
 
     glLineWidth(1.f);
     glPointSize(4.f);