From 3eb4faea1d6f42bc692de9944434670ed7c23d9f Mon Sep 17 00:00:00 2001
From: matthew <matthew@owens.tech>
Date: Sat, 18 Aug 2018 18:23:53 +0100
Subject: [PATCH] implemented rect rendering using EBOs, drawing two rectangles
with seperate shaders
---
gl/main.c | 122 +++++++++++++++++++++++---------------
gl/shaders/tri2/tri2.frag | 7 +++
gl/shaders/tri2/tri2.vert | 7 +++
3 files changed, 88 insertions(+), 48 deletions(-)
create mode 100644 gl/shaders/tri2/tri2.frag
create mode 100644 gl/shaders/tri2/tri2.vert
diff --git a/gl/main.c b/gl/main.c
index 507cf58..ef5381b 100644
--- a/gl/main.c
+++ b/gl/main.c
@@ -11,58 +11,79 @@ static int screen_width = 1280;
static int screen_height = 720;
static float vertices[] = {
- -0.5f, -0.5f, 0.0f,
- 0.5f, -0.5f, 0.0f,
- 0.0f, 0.5f, 0.0f
+ 0.0f, 0.5f, 0.0f, // top right
+ 0.0f, -0.5f, 0.0f, // bottom right
+ -1.0f, -0.5f, 0.0f, // bottom left
+ -1.0f, 0.5f, 0.0f // top left
};
-static unsigned int vbo, vao;
-static unsigned int vertShader, fragShader, shaderProgram;
-static GLchar *vertSrc = NULL;
-static GLchar *fragSrc = NULL;
+static float vertices2[] = {
+ 1.0f, 0.5f, 0.0f, // top right
+ 1.0f, -0.5f, 0.0f, // bottom right
+ 0.0f, -0.5f, 0.0f, // bottom left
+ 0.0f, 0.5f, 0.0f // top left
+};
+
+static unsigned int indices[] = {
+ 0, 1, 3,
+ 1, 2, 3
+};
-static void initTri()
+static unsigned int ebo;
+static unsigned int vbos[2], vaos[2];
+static unsigned int vertShader[2], fragShader[2], shaderProgram[2];
+static GLchar *vertSrc[2];
+static GLchar *fragSrc[2];
+
+static void initShapes()
{
- glGenBuffers(1, &vbo);
- glBindBuffer(GL_ARRAY_BUFFER, vbo);
- glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
+ glGenBuffers(2, vbos);
+ glGenVertexArrays(2, vaos);
+ glGenBuffers(1, &ebo);
- glGenVertexArrays(1, &vao);
- glBindVertexArray(vao);
-
- vertShader = glCreateShader(GL_VERTEX_SHADER);
- vertSrc = shader_load_src("tri", VERTEX);
- shader_compile(vertShader, vertSrc, "triangle vertex");
-
- fragShader = glCreateShader(GL_FRAGMENT_SHADER);
- fragSrc = shader_load_src("tri", FRAGMENT);
- shader_compile(fragShader, fragSrc, "triangle fragment");
-
- shaderProgram = glCreateProgram();
- glAttachShader(shaderProgram, vertShader);
- glAttachShader(shaderProgram, fragShader);
- glLinkProgram(shaderProgram);
-
- /*
- * The glVertexAttribPointer call is rather complex, so I will document it
- * here.
- * The 1st paramater specifies the vertex attrib to configure. We want to
- * configure the position attribute, as specified with:
- * layout (location = 0) in tri.vert.
- * The 2nd paramater specifies the size of the attribute to configure.
- * We are using a vec3 value in the shader which is composed of 3 values.
- * The 3rd specifies the data type of the paramater.
- * The 4th specifies if the value should be normalised.
- * The 5th specifies the size of the stride and the 6th is the offset.
- */
+ // first shape
+ glBindVertexArray(vaos[0]);
+ glBindBuffer(GL_ARRAY_BUFFER, vbos[0]);
+ glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3*sizeof(float), (void*)0);
glEnableVertexAttribArray(0); // param is the location of the attrib to enable.
+ glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
+ glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
+
- // cleaning up
- glDeleteShader(vertShader);
- glDeleteShader(fragShader);
- shader_free_src(vertSrc);
- shader_free_src(fragSrc);
+ // second shape
+ glBindVertexArray(vaos[1]);
+ glBindBuffer(GL_ARRAY_BUFFER, vbos[1]);
+ glBufferData(GL_ARRAY_BUFFER, sizeof(vertices2), vertices2, GL_STATIC_DRAW);
+ glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3*sizeof(float), (void*)0);
+ glEnableVertexAttribArray(0);
+ glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
+ glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
+
+ glBindVertexArray(0); // unbinding vao, since we're done
+
+ vertSrc[0] = shader_load_src("tri", VERTEX);
+ vertSrc[1] = shader_load_src("tri2", VERTEX);
+ fragSrc[0] = shader_load_src("tri", FRAGMENT);
+ fragSrc[1] = shader_load_src("tri2", FRAGMENT);
+
+ for(int i = 0; i < 2; ++i){
+ vertShader[i] = glCreateShader(GL_VERTEX_SHADER);
+ shader_compile(vertShader[i], vertSrc[i], "vertex");
+ fragShader[i] = glCreateShader(GL_FRAGMENT_SHADER);
+ shader_compile(fragShader[i], fragSrc[i], "Fragment");
+
+ shaderProgram[i] = glCreateProgram();
+ glAttachShader(shaderProgram[i], vertShader[i]);
+ glAttachShader(shaderProgram[i], fragShader[i]);
+ glLinkProgram(shaderProgram[i]);
+
+ // cleaning up
+ glDeleteShader(vertShader[i]);
+ glDeleteShader(fragShader[i]);
+ shader_free_src(vertSrc[i]);
+ shader_free_src(fragSrc[i]);
+ }
}
static bool init()
@@ -108,10 +129,15 @@ static void render()
{
glClearColor(0.2, 0.3, 0.3, 1.0);
glClear(GL_COLOR_BUFFER_BIT);
+ //glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
+
+ glUseProgram(shaderProgram[0]);
+ glBindVertexArray(vaos[0]);
+ glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
- glUseProgram(shaderProgram);
- glBindVertexArray(vao);
- glDrawArrays(GL_TRIANGLES, 0, 3);
+ glUseProgram(shaderProgram[1]);
+ glBindVertexArray(vaos[1]);
+ glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
SDL_GL_SwapWindow(window);
}
@@ -124,7 +150,7 @@ int main()
if(!init())
return -1;
- initTri();
+ initShapes();
itime = SDL_GetTicks();
diff --git a/gl/shaders/tri2/tri2.frag b/gl/shaders/tri2/tri2.frag
new file mode 100644
index 0000000..7eb0d06
--- /dev/null
+++ b/gl/shaders/tri2/tri2.frag
@@ -0,0 +1,7 @@
+#version 330 core
+out vec4 fragColor;
+
+void main()
+{
+ fragColor = vec4(0.2f, 0.5f, 1.0f, 1.0f);
+}
diff --git a/gl/shaders/tri2/tri2.vert b/gl/shaders/tri2/tri2.vert
new file mode 100644
index 0000000..0e6b9fc
--- /dev/null
+++ b/gl/shaders/tri2/tri2.vert
@@ -0,0 +1,7 @@
+#version 330 core
+layout (location = 0) in vec3 aPos;
+
+void main()
+{
+ gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);
+}
--
2.20.1