add shot-ring shader and create shot-ring attributes buffer

assets/fs/shaders/shot-ring.f.glsl

@@ -0,0 +1,5 @@
+
+void main(void)
+{
+    gl_FragColor = vec4(1.0, 0.1, 0.1, 1.0);
+}

assets/fs/shaders/shot-ring.v.glsl

@@ -0,0 +1,13 @@
+
+uniform mat4 projection;
+uniform mat4 modelview;
+uniform float scale;
+
+/* pos.xyz is position, pos.w is offset */
+attribute vec4 pos;
+
+void main(void)
+{
+    vec3 pos3 = pos.xyz * (scale + pos.w);
+    gl_Position = projection * modelview * vec4(pos3, 1);
+}

src/client/Client-gl.cc

@@ -17,6 +17,8 @@ using namespace std;
 #define SKY_DIST 2000
 #define NUM_SKY_STEPS 9
 #define LAVA_SIZE 100
+#define SHOT_RING_WIDTH 20.0f
+#define NUM_SHOT_RING_STEPS 24
 
 /* points of a horizontal hexagon 1.0 units high */
 static const float overlay_hex_attributes[][3] = {
@@ -183,6 +185,29 @@ bool Client::initgl()
         cerr << "Error creating sky attribute buffer" << endl;
         return false;
     }
+    vector<GLfloat> shot_ring_attributes((NUM_SHOT_RING_STEPS + 1) * 2 * 4);
+    for (int i = 0, idx = 0; i <= NUM_SHOT_RING_STEPS; i++)
+    {
+        double angle = i * M_PI * 2.0 / NUM_SHOT_RING_STEPS;
+        GLfloat x = sin(angle);
+        GLfloat y = cos(angle);
+        shot_ring_attributes[idx++] = x;
+        shot_ring_attributes[idx++] = y;
+        shot_ring_attributes[idx++] = 0.0f;
+        shot_ring_attributes[idx++] = 0.0f;
+
+        shot_ring_attributes[idx++] = x;
+        shot_ring_attributes[idx++] = y;
+        shot_ring_attributes[idx++] = 0.0f;
+        shot_ring_attributes[idx++] = SHOT_RING_WIDTH;
+    }
+    if (!m_shot_ring_attributes.create(GL_ARRAY_BUFFER, GL_STATIC_DRAW,
+                &shot_ring_attributes[0],
+                sizeof(shot_ring_attributes[0]) * shot_ring_attributes.size()))
+    {
+        cerr << "Error creating shot ring attributes buffer" << endl;
+        return false;
+    }
     unsigned int lava_texture_length;
     const uint8_t *lava_texture = CFS.get_file("textures/lava.jpg",
             &lava_texture_length);

src/client/Client.h

@@ -52,6 +52,7 @@ class Client
         GLBuffer m_sky_attributes;
         GLBuffer m_tex_quad_attributes;
         GLBuffer m_quad_attributes;
+        GLBuffer m_shot_ring_attributes;
         refptr<Network> m_net_client;
         bool client_has_focus;
         sf::Texture m_lava_texture;