opengl_x11

commit f86593932252ed48f084bfe7669863ead9f3d60f
parent 992a70537d196093545a564c3e357dca07791f09
Author: bsandro <email@bsandro.tech>
Date:   Wed,  7 Jan 2026 01:01:26 +0200

rotating in geometry shader squares

Diffstat:
M
obj2d.c
 | 
19
++++++++++++++++---

1 file changed, 16 insertions(+), 3 deletions(-)
diff --git a/obj2d.c b/obj2d.c
@@ -51,19 +51,33 @@ static const GLchar *geometrySrc = R"(
 layout(points) in;
 layout(line_strip,max_vertices=6) out;
 in vec3 dotColor[];
+uniform double iTime;
 out vec3 fColor;
+
+mat2 rotate(float a) {
+    float s = sin(a);
+    float c = cos(a);
+    return mat2(c, -s,
+                s,  c);
+}
+
 void main() {
     fColor = dotColor[0];
     vec4 p = gl_in[0].gl_Position;
-    gl_Position = p+vec4(-0.1, -0.1, 0.0, 0.0);
+    vec4 p1 = p+vec4(-0.1, -0.1, 0.0, 0.0);
+    p1 = vec4(p.xy+rotate(float(iTime))*(p1.xy - p.xy), 0.0, 1.0);
+    gl_Position = p1;
     EmitVertex();
     gl_Position = p+vec4(0.1, -0.1, 0.0, 0.0);
+    gl_Position = vec4(p.xy+rotate(float(iTime))*(gl_Position.xy - p.xy), 0.0, 1.0);
     EmitVertex();
     gl_Position = p+vec4(0.1, 0.1, 0.0, 0.0);
+    gl_Position = vec4(p.xy+rotate(float(iTime))*(gl_Position.xy - p.xy), 0.0, 1.0);
     EmitVertex();
     gl_Position = p+vec4(-0.1, 0.1, 0.0, 0.0);
+    gl_Position = vec4(p.xy+rotate(float(iTime))*(gl_Position.xy - p.xy), 0.0, 1.0);
     EmitVertex();
-    gl_Position = p+vec4(-0.1, -0.1, 0.0, 0.0);
+    gl_Position = p1;
     EmitVertex();
     EndPrimitive();
 }
@@ -132,7 +146,6 @@ struct vec2 rand_shift(void) {
 
 int main(void) {
     srand(time(0));
-    printf("rngesus: %d, %d\n", rand() % 5, RAND_MAX);
     Display *dpy = XOpenDisplay(NULL);
     XSetWindowAttributes swa;
     Window win;