Work on OpenGL rendering environment.

src/glutils.cpp

@@ -0,0 +1,104 @@
+#include <cstdint>
+#include <memory>
+#include <vector>
+#include <GL/glew.h>
+#include <cstring>
+#include <glog/logging.h>
+#include "glutils.hpp"
+
+using namespace fmri;
+using namespace std;
+
+/**
+ * Utility function to send OpenGL info dumps to the log
+ *
+ * @param object The GLObject to get info for
+ * @param glGet__iv The function to query log length with
+ * @param glGet__InfoLog The function to get the log with
+ */
+static void show_info_log(
+        GLuint object,
+        PFNGLGETSHADERIVPROC glGet__iv,
+        PFNGLGETSHADERINFOLOGPROC glGet__InfoLog
+)
+{
+    GLint log_length;
+    glGet__iv(object, GL_INFO_LOG_LENGTH, &log_length);
+    unique_ptr<char[]> log(new char[log_length]);
+    glGet__InfoLog(object, log_length, nullptr, log.get());
+
+    LOG(INFO) << log.get() << endl;
+}
+
+GLuint fmri::loadTexture(DType const *data, unsigned int width, unsigned int height)
+{
+    // Load and scale texture
+    vector<DType> textureBuffer(data, data + (width * height));
+    rescale(textureBuffer.begin(), textureBuffer.end(), 0, 1);
+
+    const float color[] = {0, 0, 0}; // Background color for textures.
+    GLuint texture;
+    glGenTextures(1, &texture);
+
+    glBindTexture(GL_TEXTURE_2D, texture);
+
+    // Set up (lack of) repetition
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_R, GL_CLAMP_TO_BORDER);
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_BORDER);
+    glTexParameterfv(GL_TEXTURE_2D, GL_TEXTURE_BORDER_COLOR, color);
+
+    static_assert(sizeof(DType) == 4); // verify data type for texture.
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_R32F, 2, 2, 0, GL_R32F, GL_FLOAT, textureBuffer.data());
+
+    // Set up texture scaling
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR); // Use mipmapping for scaling down
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); // Use nearest pixel when scaling up.
+
+    glGenerateMipmap(GL_TEXTURE_2D);
+
+
+    return texture;
+}
+
+void fmri::changeWindowSize(int w, int h)
+{
+    // Prevent a divide by zero, when window is too short
+    // (you cant make a window of zero width).
+    if (h == 0)
+        h = 1;
+
+    float ratio = w * 1.0f / h;
+
+    // Use the Projection Matrix
+    glMatrixMode(GL_PROJECTION);
+
+    // Reset Matrix
+    glLoadIdentity();
+
+    // Set the viewport to be the entire window
+    glViewport(0, 0, w, h);
+
+    // Set the correct perspective.
+    gluPerspective(45.0f, ratio, 0.1f, 100.0f);
+
+    // Get Back to the Modelview
+    glMatrixMode(GL_MODELVIEW);
+}
+
+GLuint fmri::compileShader(GLenum type, char const *source)
+{
+    GLuint shader = glCreateShader(type);
+    auto length = static_cast<GLint>(strlen(source));
+    GLint compileOK;
+
+    glShaderSource(shader, 1, &source, &length);
+    glCompileShader(shader);
+
+    glGetShaderiv(shader, GL_COMPILE_STATUS, &compileOK);
+    if (!compileOK) {
+        LOG(WARNING) << "Failed to compile " << source << endl;
+        show_info_log(shader, glGetShaderiv, glGetShaderInfoLog);
+        glDeleteShader(shader);
+        abort();
+    }
+}