# OpenGL Matrix operation order causing positioning problems!

This topic is 1895 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

## Recommended Posts

Hi All,

I'm currently having some positioning problems using OpenGL and LWJGL, but figured this would be generic enough for the OGL forum!

I wanted to know whether my method for positioning objects in the world is correct, as I'm not sure my matrix operations are in the right order.

For every object that's placed in the world, I'm doing the following:[list]
[*]Load the Identity Matrix (reset everything)
[*]Translate to the [b]camera's [/b]X, Y, Z position
[*]Rotate the camera around the X and Y axes (I'm not doing Z rolling)
[*]Translate to the [b]object's[/b] X, Y, Z position
[*]Rotate the [b]object [/b]around the X, Y, Z axes.
[/list]

I keep tweaking things and somehow getting it to work, but I'd like to know the de-facto method for accomplishing this. I'm aware that you're normally supposed to rotate before a translation, but I think it works different in LWJGL? I might be wrong on this, though.

Every object has its own X, Y, Z position in the world, as has the camera. But the whole interation between them has confused me to no end now!

Thanks for any assistance anyone can offer : ) Edited by PixelPrime11

##### Share on other sites
Matrix multiplication is not commutative, so m1 * m2 != m2 * m1. The correct order to use will depend on the matrix library you're using.

##### Share on other sites
I'm not sure what you mean by which Matrix Library, unless you mean LWJGL's implementation of this?

The methods I use to accomplish the transformations are as follows:

glTransform3f(camera.x, camera.y, camera.z);

glRotate3f(camera.yaw, 0.0f, 1.0f, 0.0f);

glRotate3f(camera.pitch, 1.0f, 0.0f, 0.0f);
[/source]

So, if I were trying to draw an object in the world, I'd call the above code first, then this:

[source lang="java"]
// move to the object's coordinates
glTranslate3f(position.x, position.y, position.z);

// rotate the object (Y axis only)
glRotate3f(rotation.y, 0.0f, 1.0f, 0.0f);

// draw the object

// vertex draw operations

glEnd();[/source] Edited by PixelPrime11

##### Share on other sites
That doesn't seem to make sense. You want to apply the [b]inverse[/b] of your camera transformation. There is no actual camera and the point is to move the world in the opposite way, which means reverse direction and reverse order for your camera transformations. You might also want to reconsider your approach using Euler angles sooner rather than later (and no, that doesn't mean using quaternions, it means not using Euler angles).

Unless you're going for a straight forward ground based first person view you will eventually run into a wall when you come to the point where the order in which rotations where applied is actually important.

• 11
• 9
• 16
• 18
• 10
• ### Similar Content

• i got error 1282 in my code.
#version 450 core layout(location=0) in vec3 inPos; layout(location=1) in vec2 inTexCoord; out vec2 TexCoord; void main() { gl_Position=vec4(inPos,1.0); TexCoord=inTexCoord; } and the fragment shader
#version 450 core in vec2 TexCoord; uniform sampler2D inTextureOne; uniform sampler2D inTextureTwo; out vec4 FragmentColor; void main() { FragmentColor=mix(texture(inTextureOne,TexCoord),texture(inTextureTwo,TexCoord),0.2); } I was expecting awesomeface.png on top of container.jpg

• By khawk
We've just released all of the source code for the NeHe OpenGL lessons on our Github page at https://github.com/gamedev-net/nehe-opengl. code - 43 total platforms, configurations, and languages are included.
Now operated by GameDev.net, NeHe is located at http://nehe.gamedev.net where it has been a valuable resource for developers wanting to learn OpenGL and graphics programming.

View full story
• By TheChubu
The Khronos™ Group, an open consortium of leading hardware and software companies, announces from the SIGGRAPH 2017 Conference the immediate public availability of the OpenGL® 4.6 specification. OpenGL 4.6 integrates the functionality of numerous ARB and EXT extensions created by Khronos members AMD, Intel, and NVIDIA into core, including the capability to ingest SPIR-V™ shaders.
SPIR-V is a Khronos-defined standard intermediate language for parallel compute and graphics, which enables content creators to simplify their shader authoring and management pipelines while providing significant source shading language flexibility. OpenGL 4.6 adds support for ingesting SPIR-V shaders to the core specification, guaranteeing that SPIR-V shaders will be widely supported by OpenGL implementations.
OpenGL 4.6 adds the functionality of these ARB extensions to OpenGL’s core specification:
GL_ARB_gl_spirv and GL_ARB_spirv_extensions to standardize SPIR-V support for OpenGL GL_ARB_indirect_parameters and GL_ARB_shader_draw_parameters for reducing the CPU overhead associated with rendering batches of geometry GL_ARB_pipeline_statistics_query and GL_ARB_transform_feedback_overflow_querystandardize OpenGL support for features available in Direct3D GL_ARB_texture_filter_anisotropic (based on GL_EXT_texture_filter_anisotropic) brings previously IP encumbered functionality into OpenGL to improve the visual quality of textured scenes GL_ARB_polygon_offset_clamp (based on GL_EXT_polygon_offset_clamp) suppresses a common visual artifact known as a “light leak” associated with rendering shadows GL_ARB_shader_atomic_counter_ops and GL_ARB_shader_group_vote add shader intrinsics supported by all desktop vendors to improve functionality and performance GL_KHR_no_error reduces driver overhead by allowing the application to indicate that it expects error-free operation so errors need not be generated In addition to the above features being added to OpenGL 4.6, the following are being released as extensions:
GL_KHR_parallel_shader_compile allows applications to launch multiple shader compile threads to improve shader compile throughput WGL_ARB_create_context_no_error and GXL_ARB_create_context_no_error allow no error contexts to be created with WGL or GLX that support the GL_KHR_no_error extension “I’m proud to announce OpenGL 4.6 as the most feature-rich version of OpenGL yet. We've brought together the most popular, widely-supported extensions into a new core specification to give OpenGL developers and end users an improved baseline feature set. This includes resolving previous intellectual property roadblocks to bringing anisotropic texture filtering and polygon offset clamping into the core specification to enable widespread implementation and usage,” said Piers Daniell, chair of the OpenGL Working Group at Khronos. “The OpenGL working group will continue to respond to market needs and work with GPU vendors to ensure OpenGL remains a viable and evolving graphics API for all its customers and users across many vital industries.“
The OpenGL 4.6 specification can be found at https://khronos.org/registry/OpenGL/index_gl.php. The GLSL to SPIR-V compiler glslang has been updated with GLSL 4.60 support, and can be found at https://github.com/KhronosGroup/glslang.
Sophisticated graphics applications will also benefit from a set of newly released extensions for both OpenGL and OpenGL ES to enable interoperability with Vulkan and Direct3D. These extensions are named:
GL_EXT_memory_object GL_EXT_memory_object_fd GL_EXT_memory_object_win32 GL_EXT_semaphore GL_EXT_semaphore_fd GL_EXT_semaphore_win32 GL_EXT_win32_keyed_mutex They can be found at: https://khronos.org/registry/OpenGL/index_gl.php
Industry Support for OpenGL 4.6
“With OpenGL 4.6 our customers have an improved set of core features available on our full range of OpenGL 4.x capable GPUs. These features provide improved rendering quality, performance and functionality. As the graphics industry’s most popular API, we fully support OpenGL and will continue to work closely with the Khronos Group on the development of new OpenGL specifications and extensions for our customers. NVIDIA has released beta OpenGL 4.6 drivers today at https://developer.nvidia.com/opengl-driver so developers can use these new features right away,” said Bob Pette, vice president, Professional Graphics at NVIDIA.
"OpenGL 4.6 will be the first OpenGL release where conformant open source implementations based on the Mesa project will be deliverable in a reasonable timeframe after release. The open sourcing of the OpenGL conformance test suite and ongoing work between Khronos and X.org will also allow for non-vendor led open source implementations to achieve conformance in the near future," said David Airlie, senior principal engineer at Red Hat, and developer on Mesa/X.org projects.

View full story
• By _OskaR
Hi,
I have an OpenGL application but without possibility to wite own shaders.
I need to perform small VS modification - is possible to do it in an alternative way? Do we have apps or driver modifictions which will catch the shader sent to GPU and override it?
• By xhcao
Does sync be needed to read texture content after access texture image in compute shader?
My simple code is as below,
glUseProgram(program.get());
glBindImageTexture(0, texture[0], 0, GL_FALSE, 3, GL_READ_ONLY, GL_R32UI);
glBindImageTexture(1, texture[1], 0, GL_FALSE, 4, GL_WRITE_ONLY, GL_R32UI);
glDispatchCompute(1, 1, 1);
// Does sync be needed here?
glUseProgram(0);