Add scene/pick shaders and ShaderProgram compiler

CityDoctorParent/Extensions/CityDoctorGUI/src/main/java/de/hft/stuttgart/citydoctor2/gui/gl/ShaderProgram.java

+package de.hft.stuttgart.citydoctor2.gui.gl;
+
+import com.jogamp.opengl.GL3;
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.UncheckedIOException;
+import java.nio.charset.StandardCharsets;
+import java.util.stream.Collectors;
+
+/** Compiles and links a GLSL program from classpath resources next to this class. */
+public class ShaderProgram {
+
+    private final int program;
+
+    public ShaderProgram(GL3 gl, String vertexResource, String fragmentResource) {
+        int vs = compile(gl, GL3.GL_VERTEX_SHADER, read(vertexResource));
+        int fs = compile(gl, GL3.GL_FRAGMENT_SHADER, read(fragmentResource));
+        program = gl.glCreateProgram();
+        gl.glAttachShader(program, vs);
+        gl.glAttachShader(program, fs);
+        gl.glLinkProgram(program);
+        checkLink(gl, program);
+        gl.glDeleteShader(vs);
+        gl.glDeleteShader(fs);
+    }
+
+    public void use(GL3 gl) { gl.glUseProgram(program); }
+
+    public int uniform(GL3 gl, String name) { return gl.glGetUniformLocation(program, name); }
+
+    public void dispose(GL3 gl) { gl.glDeleteProgram(program); }
+
+    private static int compile(GL3 gl, int type, String src) {
+        int shader = gl.glCreateShader(type);
+        gl.glShaderSource(shader, 1, new String[]{src}, new int[]{src.length()}, 0);
+        gl.glCompileShader(shader);
+        int[] status = new int[1];
+        gl.glGetShaderiv(shader, GL3.GL_COMPILE_STATUS, status, 0);
+        if (status[0] == 0) {
+            throw new IllegalStateException("Shader compile failed: " + infoLog(gl, shader, true));
+        }
+        return shader;
+    }
+
+    private static void checkLink(GL3 gl, int program) {
+        int[] status = new int[1];
+        gl.glGetProgramiv(program, GL3.GL_LINK_STATUS, status, 0);
+        if (status[0] == 0) {
+            throw new IllegalStateException("Program link failed: " + infoLog(gl, program, false));
+        }
+    }
+
+    private static String infoLog(GL3 gl, int handle, boolean shader) {
+        int[] len = new int[1];
+        if (shader) {
+            gl.glGetShaderiv(handle, GL3.GL_INFO_LOG_LENGTH, len, 0);
+        } else {
+            gl.glGetProgramiv(handle, GL3.GL_INFO_LOG_LENGTH, len, 0);
+        }
+        byte[] log = new byte[Math.max(1, len[0])];
+        if (shader) {
+            gl.glGetShaderInfoLog(handle, log.length, new int[1], 0, log, 0);
+        } else {
+            gl.glGetProgramInfoLog(handle, log.length, new int[1], 0, log, 0);
+        }
+        return new String(log, StandardCharsets.UTF_8);
+    }
+
+    private static String read(String resource) {
+        try (InputStream in = ShaderProgram.class.getResourceAsStream(resource)) {
+            if (in == null) {
+                throw new IllegalStateException("Shader resource not found: " + resource);
+            }
+            try (BufferedReader r = new BufferedReader(new InputStreamReader(in, StandardCharsets.UTF_8))) {
+                return r.lines().collect(Collectors.joining("\n"));
+            }
+        } catch (IOException e) {
+            throw new UncheckedIOException(e);
+        }
+    }
+}

CityDoctorParent/Extensions/CityDoctorGUI/src/main/resources/de/hft/stuttgart/citydoctor2/gui/gl/pick.frag

+#version 330 core
+flat in int vId;
+out vec4 fragColor;
+void main() {
+    int id = vId;
+    float r = float( id        & 0xFF) / 255.0;
+    float g = float((id >> 8)  & 0xFF) / 255.0;
+    float b = float((id >> 16) & 0xFF) / 255.0;
+    fragColor = vec4(r, g, b, 1.0);
+}

CityDoctorParent/Extensions/CityDoctorGUI/src/main/resources/de/hft/stuttgart/citydoctor2/gui/gl/pick.vert

+#version 330 core
+layout(location = 0) in vec3 aPos;
+layout(location = 2) in int  aId;
+uniform mat4 uMVP;
+flat out int vId;
+void main() {
+    gl_Position = uMVP * vec4(aPos, 1.0);
+    vId = aId;
+}

CityDoctorParent/Extensions/CityDoctorGUI/src/main/resources/de/hft/stuttgart/citydoctor2/gui/gl/scene.frag

+#version 330 core
+in vec3 vColor;
+flat in int vSelected;
+out vec4 fragColor;
+void main() {
+    vec3 c = vColor;
+    if (vSelected == 1) {
+        c = mix(c, vec3(1.0, 0.0, 0.0), 0.6);
+    }
+    fragColor = vec4(c, 1.0);
+}

CityDoctorParent/Extensions/CityDoctorGUI/src/main/resources/de/hft/stuttgart/citydoctor2/gui/gl/scene.vert

+#version 330 core
+layout(location = 0) in vec3 aPos;
+layout(location = 1) in vec3 aColor;
+layout(location = 2) in int  aId;
+uniform mat4 uMVP;
+uniform int  uSelectedId;
+out vec3 vColor;
+flat out int vSelected;
+void main() {
+    gl_Position = uMVP * vec4(aPos, 1.0);
+    vColor = aColor;
+    vSelected = (aId == uSelectedId) ? 1 : 0;
+}