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      using System; using OpenTK; using OpenTK.Input; using OpenTK.Graphics; using OpenTK.Graphics.OpenGL4; using System.Drawing; using System.Reflection; namespace Tutorial_05 { class Game : GameWindow { private static int WIDTH = 1200; private static int HEIGHT = 720; private static KeyboardState keyState; private int vaoID; private int vboID; private int iboID; private Vector3[] vertices = { new Vector3(-0.5f, 0.5f, 0.0f), // V0 new Vector3(-0.5f, -0.5f, 0.0f), // V1 new Vector3(0.5f, -0.5f, 0.0f), // V2 new Vector3(0.5f, 0.5f, 0.0f) // V3 }; private Vector2[] texcoords = { new Vector2(0, 0), new Vector2(0, 1), new Vector2(1, 1), new Vector2(1, 0) }; private int[] indices = { 0, 1, 3, 3, 1, 2 }; private string vertsrc = @"#version 450 core in vec3 position; in vec2 textureCoords; out vec2 pass_textureCoords; void main(void) { gl_Position = vec4(position, 1.0); pass_textureCoords = textureCoords; }"; private string fragsrc = @"#version 450 core in vec2 pass_textureCoords; out vec4 out_color; uniform sampler2D textureSampler; void main(void) { out_color = texture(textureSampler, pass_textureCoords); }"; private int programID; private int vertexShaderID; private int fragmentShaderID; private int textureID; private Bitmap texsrc; public Game() : base(WIDTH, HEIGHT, GraphicsMode.Default, "Tutorial 05 - Texturing", GameWindowFlags.Default, DisplayDevice.Default, 4, 5, GraphicsContextFlags.Default) { } protected override void OnLoad(EventArgs e) { base.OnLoad(e); CursorVisible = true; GL.GenVertexArrays(1, out vaoID); GL.BindVertexArray(vaoID); GL.GenBuffers(1, out vboID); GL.BindBuffer(BufferTarget.ArrayBuffer, vboID); GL.BufferData(BufferTarget.ArrayBuffer, (IntPtr)(vertices.Length * Vector3.SizeInBytes), vertices, BufferUsageHint.StaticDraw); GL.GenBuffers(1, out iboID); GL.BindBuffer(BufferTarget.ElementArrayBuffer, iboID); GL.BufferData(BufferTarget.ElementArrayBuffer, (IntPtr)(indices.Length * sizeof(int)), indices, BufferUsageHint.StaticDraw); vertexShaderID = GL.CreateShader(ShaderType.VertexShader); GL.ShaderSource(vertexShaderID, vertsrc); GL.CompileShader(vertexShaderID); fragmentShaderID = GL.CreateShader(ShaderType.FragmentShader); GL.ShaderSource(fragmentShaderID, fragsrc); GL.CompileShader(fragmentShaderID); programID = GL.CreateProgram(); GL.AttachShader(programID, vertexShaderID); GL.AttachShader(programID, fragmentShaderID); GL.LinkProgram(programID); // Loading texture from embedded resource texsrc = new Bitmap(Assembly.GetEntryAssembly().GetManifestResourceStream("Tutorial_05.example.png")); textureID = GL.GenTexture(); GL.BindTexture(TextureTarget.Texture2D, textureID); GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMagFilter, (int)All.Linear); GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMinFilter, (int)All.Linear); GL.TexImage2D(TextureTarget.Texture2D, 0, PixelInternalFormat.Rgba, texsrc.Width, texsrc.Height, 0, PixelFormat.Bgra, PixelType.UnsignedByte, IntPtr.Zero); System.Drawing.Imaging.BitmapData bitmap_data = texsrc.LockBits(new Rectangle(0, 0, texsrc.Width, texsrc.Height), System.Drawing.Imaging.ImageLockMode.ReadOnly, System.Drawing.Imaging.PixelFormat.Format32bppRgb); GL.TexSubImage2D(TextureTarget.Texture2D, 0, 0, 0, texsrc.Width, texsrc.Height, PixelFormat.Bgra, PixelType.UnsignedByte, bitmap_data.Scan0); texsrc.UnlockBits(bitmap_data); GL.Enable(EnableCap.Texture2D); GL.BufferData(BufferTarget.TextureBuffer, (IntPtr)(texcoords.Length * Vector2.SizeInBytes), texcoords, BufferUsageHint.StaticDraw); GL.BindAttribLocation(programID, 0, "position"); GL.BindAttribLocation(programID, 1, "textureCoords"); } protected override void OnResize(EventArgs e) { base.OnResize(e); GL.Viewport(0, 0, ClientRectangle.Width, ClientRectangle.Height); } protected override void OnUpdateFrame(FrameEventArgs e) { base.OnUpdateFrame(e); keyState = Keyboard.GetState(); if (keyState.IsKeyDown(Key.Escape)) { Exit(); } } protected override void OnRenderFrame(FrameEventArgs e) { base.OnRenderFrame(e); // Prepare for background GL.Clear(ClearBufferMask.ColorBufferBit); GL.ClearColor(Color4.Red); // Draw traingles GL.EnableVertexAttribArray(0); GL.EnableVertexAttribArray(1); GL.BindVertexArray(vaoID); GL.UseProgram(programID); GL.BindBuffer(BufferTarget.ArrayBuffer, vboID); GL.VertexAttribPointer(0, 3, VertexAttribPointerType.Float, false, 0, IntPtr.Zero); GL.ActiveTexture(TextureUnit.Texture0); GL.BindTexture(TextureTarget.Texture3D, textureID); GL.BindBuffer(BufferTarget.ElementArrayBuffer, iboID); GL.DrawElements(BeginMode.Triangles, indices.Length, DrawElementsType.UnsignedInt, 0); GL.DisableVertexAttribArray(0); GL.DisableVertexAttribArray(1); SwapBuffers(); } protected override void OnClosed(EventArgs e) { base.OnClosed(e); GL.DeleteVertexArray(vaoID); GL.DeleteBuffer(vboID); } } } I can not remember where do I add GL.Uniform2();
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OpenGL avoid loosing Stacked Transformations on Load identity matrix

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Hi guys,

When I use to code in regular old opengl it had glLoadIdentity() which would help me translate my object , load Identity matrix and then rotate it around its own axis.

when stacking translation and rotation together an object will not rotate around it`s own origin, but rather (around the initial point it was translated from).(which according to matrix math it is supposed to)

How do I translate an object and then rotatate it about it`s own origin using glm library or even better manually since I want to understand how it can be done. I presume loadIdentity resets the model matrix to identity matrix but then you will loose your previous translation .. I cannot seem to figure out how you could do it manually here is my code:

RenderScene

void renderScene()
{
glm::mat4 ModelViewProject;

	glm::mat4 View;

	glm::mat4 Model;
	
	glm::mat4 Projection = glm::perspective(45.0f, 1024.0f / 768.0f, 0.1f, 10.0f);


	glm::mat4 rotation = glm::rotate(Model, angle, glm::vec3(1, 0, 0));

	Model *= rotation;

	rotation = loadIdentity(); 

	glm::mat4 transRotation = glm::translate(rotation, glm::vec3(xCh, yCh, zCh));
	

	Model *= transRotation;
View = glm::lookAt(glm::vec3(0, 0, 2), glm::vec3(0, 0, 0), glm::vec3(0.0, 1.0, 0.0));

ModelViewProject = Projection * View *  Model;

GLint transform = glGetUniformLocation(programId, "ModelViewProject");

	glUniformMatrix4fv(transform, 1, false, glm::value_ptr(ModelViewProject));;


	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	glClearColor(0.0, 0.0, 0.0, 1.0);
	
	glDrawArrays(GL_TRIANGLES, 0, 6);

	glutSwapBuffers();
	}


Vertex Initial position

 


void init()
{
	int z = 1.0f;

	GLfloat vertices[] =
	{
		
		0.999999f, 1.000000f, 1.0f,
		 0.0f, 0.0f, 1.0f,
		 -1.000000f, 1.000000f, 1.0f,
		1.0f, 1.0f, 0.0f,
		-1.000000f, -1.000000f, 1.0f,
		0.0f, 1.0f, 1.0f, // colors

		1.000000f, -1.000000f, 1.0f,
		1.0f, 1.0f, 0.4f,
		0.999999f, 1.000000f, 1.0f,
		1.0f, 0.8f, 0.4f,
		-1.000000f, -1.000000f, 1.0f,
		0.7f, 0.8f, 0.4f,
};

	GLint FragmentShaderColorId;
	GLint VertexId;

	VertexId = glGetAttribLocation(programId, "position");

	FragmentShaderColorId = glGetAttribLocation(programId, "ColorIn");
	glEnable(GL_DEPTH_TEST);


	GLuint myBuffId = 0;

	glGenBuffers(1, &myBuffId);

	glEnableVertexAttribArray(VertexId);

	glBindBuffer(GL_ARRAY_BUFFER, myBuffId);

	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

	glVertexAttribPointer(VertexId, 3, GL_FLOAT, GL_FALSE, sizeof(float) * 6, 0);

	glEnableVertexAttribArray(FragmentShaderColorId);

	glVertexAttribPointer(FragmentShaderColorId, 3, GL_FLOAT, GL_FALSE, sizeof(float) * 6, (char *)(sizeof(float) * 3));  // stride of 5 floats describing my colors starting at position 2


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instead of using loadIdentity() why when you do your translation like say
glm::mat4 translation = glm::translate(glm::mat4(1.0f), glm::vec3(x, y, z));
The mat4(1.0f) is an identity matrix so it leaves your rotation matrix intact

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Ok, when I try to multiply the translation with the (Model * View * Projection) and then the rotation with the translated (Model * View * Projection) it gives me the same result.

 

glm::mat4 ModelViewProject;

	glm::mat4 View;

	glm::mat4 Model;
	
	glm::mat4 Projection = glm::perspective(45.0f, 1024.0f / 768.0f, 0.1f, 10.0f);

	glm::mat4 translate = glm::translate(glm::mat4(1.0), glm::vec3(xCh, yCh, zCh));



	Model *= translate;


	glm::mat4 rotation = glm::rotate(glm::mat4(1.0), angle, glm::vec3(1, 0, 0));


	Model *= rotation;

View = glm::lookAt(glm::vec3(0, 0, 2), glm::vec3(0, 0, 0), glm::vec3(0.0, 1.0, 0.0));

ModelViewProject = Projection * View *  Model;
	

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glm::mat4 translate = glm::translate(glm::mat4(1.0), glm::vec3(xCh, yCh, zCh));



Model *= translate;


glm::mat4 rotation = glm::rotate(glm::mat4(1.0), angle, glm::vec3(1, 0, 0));


Model *= rotation;

View = glm::lookAt(glm::vec3(0, 0, 2), glm::vec3(0, 0, 0), glm::vec3(0.0, 1.0, 0.0));

You have a lot of mix and match values here i dont know if it has been improved but glm never liked that so it might be worth changing your 1 to a 1.0f or a 1.f the same with your other numbers such as 0 and 2 to 0.0f and 2.0f

 

With matrix math aswell i believe the order is Scale * Rotation * Translation so in c++ it would be

model = translation * rotation * scale;

 

Then after doing that do your

modelViewProject = projection * view * model;

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Hi, thanks for your reply, I followed what you said, now the object rotates but still it rotates in an arc sort of way( yet less of an arc than before) but not around its own axis.
The most surprising thing is it rotates in an arc way even if you do not apply translation (just rotation).....any ideas ?
 

void renderScene()
{
glm::mat4 ModelViewProject(1.0f);

	glm::mat4 View(1.0f);

	glm::mat4 Model(1.0f);
	
	glm::mat4 Projection = glm::perspective(45.0f, 1024.0f / 768.0f, 0.1f, 10.0f);

	glm::mat4 translate = glm::translate(glm::mat4(1.0f), glm::vec3(xCh, yCh, zCh));

glm::mat4 rotation = glm::rotate(glm::mat4(1.0), angle, glm::vec3(1.0f, 0.0f, 0.0f));


	Model = translate * rotation;

	View = glm::lookAt(glm::vec3(0.0f, 0.0f, 2.0f), glm::vec3(0.0f, 0.0f, 0.0f), glm::vec3(0.0f, 1.0f, 0.0f));

	ModelViewProject = Projection * View *  Model;

	GLint transform = glGetUniformLocation(programId, "ModelViewProject");

	glUniformMatrix4fv(transform, 1, false, glm::value_ptr(ModelViewProject));;


	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
	
	glDrawArrays(GL_TRIANGLES, 0, 6);

	glutSwapBuffers();
}
	


 

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