Introducing scene graph

2025-12-11 18:34:58 +01:00 · 2020-03-31 17:01:33 +02:00
parent cf5a3b3fc9
commit 2fc01e8435
17 changed files with 837 additions and 184 deletions
--- a/snippets.cpp
+++ b/snippets.cpp
@@ -0,0 +1,98 @@
+GLuint loadPNG(const char *imagepath, float *aspectrato)
+{
+    int w, h, n, image;
+    /* FIXME: remove once the example supports gl3 and/or gles2 */
+    g_setenv ("GST_GL_API", "opengl", FALSE);
+	unsigned char* img;
+    *aspectrato = 1.f;
+
+	img = stbi_load(imagepath, &w, &h, &n, 3);
+	if (img == NULL) {
+		printf("Failed to load png - %s\n", stbi_failure_reason());
+	 return 0;
+	}
+    GLuint tex;
+    glGenTextures(1, &tex);
+
+	glBindTexture( GL_TEXTURE_2D, tex);
+	glPixelStorei(GL_UNPACK_ALIGNMENT, 3);
+
+    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+
+    //glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
+	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, w, h, 0, GL_RGB, GL_UNSIGNED_BYTE, img);
+
+	stbi_image_free(img);
+	glBindTexture( GL_TEXTURE_2D, 0);
+
+    *aspectrato = static_cast<float>(w) / static_cast<float>(h);
+    return tex;
+}
+
+
+void create_square_glm(unsigned int &vbo, unsigned int &vao, unsigned int &ebo)
+{
+    std::vector<glm::vec3>     points_;
+    std::vector<glm::vec3>     colors_;
+    std::vector<glm::vec2>     texCoords_;
+    std::vector<unsigned int>  indices_;
+
+    // point 0
+    points_.push_back( glm::vec3( -1.f, -1.f, 0.f ) );
+    colors_.push_back( glm::vec3( 1.f, 0.f, 0.f ) );
+    texCoords_.push_back( glm::vec2( 0.f, 1.f ) );
+    // point 1
+    points_.push_back( glm::vec3( -1.f, 1.f, 0.f ) );
+    colors_.push_back( glm::vec3( 1.f, 1.f, 1.f ) );
+    texCoords_.push_back( glm::vec2( 0.f, 0.f ) );
+    // point 2
+    points_.push_back( glm::vec3( 1.f, -1.f, 0.f ) );
+    colors_.push_back( glm::vec3( 1.f, 1.f, 1.f ) );
+    texCoords_.push_back( glm::vec2( 1.f, 1.f ) );
+    // point 3
+    points_.push_back( glm::vec3( 1.f, 1.f, 0.f ) );
+    colors_.push_back( glm::vec3( 0.f, 1.f, 0.f ) );
+    texCoords_.push_back( glm::vec2( 1.f, 0.f ) );
+    // indices
+    indices_.push_back ( 0 );
+    indices_.push_back ( 1 );
+    indices_.push_back ( 2 );
+    indices_.push_back ( 3 );
+
+    // create the opengl objects
+    glGenVertexArrays(1, &vao);
+    glGenBuffers(1, &vbo);
+    glGenBuffers(1, &ebo);
+    glBindVertexArray(vao);
+
+    // compute the memory needs for points normals and indicies
+    std::size_t sizeofPoints = sizeof(glm::vec3) * points_.size();
+    std::size_t sizeofColors = sizeof(glm::vec3) * colors_.size();
+    std::size_t sizeofTexCoords = sizeof(glm::vec2) * texCoords_.size();
+
+    // bind vertext array and its buffer
+    glBindBuffer(GL_ARRAY_BUFFER, vbo);
+    glBufferData(GL_ARRAY_BUFFER, sizeofPoints + sizeofColors + sizeofTexCoords, NULL, GL_STATIC_DRAW);
+    glBufferSubData( GL_ARRAY_BUFFER, 0, sizeofPoints, &points_[0] );
+    glBufferSubData( GL_ARRAY_BUFFER, sizeofPoints, sizeofColors, &colors_[0] );
+    glBufferSubData( GL_ARRAY_BUFFER, sizeofPoints + sizeofColors, sizeofTexCoords, &texCoords_[0] );
+
+    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
+    int sizeofIndices = indices_.size()*sizeof(unsigned int);
+    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeofIndices, &(indices_[0]), GL_STATIC_DRAW);
+
+    // explain how to read attributes 0, 1 and 2 (for point, color and textcoord respectively)
+    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(glm::vec3), (void *)0);
+    glEnableVertexAttribArray(0);
+    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, sizeof(glm::vec3), (void *)(sizeofPoints) );
+    glEnableVertexAttribArray(1);
+    glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, sizeof(glm::vec2), (void *)(sizeofPoints + sizeofColors) );
+    glEnableVertexAttribArray(2);
+
+    // done
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+    glBindVertexArray(0);
+
+}
+
+