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OpenGL why did M$ choose left-hand coordinate?

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In mathematics and opengl, coordinates are of right-hand. But, I wonder why did M$ choose left-hand coordinate, so give confusion to programmers? [Edited by - creavol on August 1, 2005 7:00:49 AM]

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Wait...what? If they're all left-hand, what's the problem?

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In mathematics, coordinates are either right- or left-handed, and must be specified for completeness. Consequently, Microsoft, or any other entity, can pick whichever coordinate system they prefer.

I was taught both left- and right-handed coordinate systems in secondary school, including corresponding variants to the corkscrew and "right-hand rule." Consequently, I say your education is deficient.

Have a nice day.

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Quote:
Original post by creavol
In mathematics and opengl, coordinates are of left-hand.


Are you sure? I'm pretty sure mathematicians use right-handed systems. Don't quote me on that though.

Quote:

But, I wonder why did M$ choose left-hand coordinate, so give confusion to programmers?

I don't know the reasons behind it, but IIRC D3DX provides functions for converting between right and left-handedness. But don't quote me on that either. [smile]

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I'm not the greatest "pure" mathemagician, but my understanding of left vs right is that it's simply 2 different ways of doing the same thing. At least, for the reasonably simple stuff - maybe it makes differences at the theoretical/complex level [grin]

Quote:
Original post by nilkn
IIRC D3DX provides functions for converting between right and left-handedness. But don't quote me on that either. [smile]

Too late, I just quoted you on it [smile] - But you are right, D3DX offers "LH" (Left Hand) and "RH" (Right Hand) flavours of the projection and view matrix functions:


D3DXMatrixLookAtLH or D3DXMatrixLookAtRH
D3DXMatrixOrthoLH or D3DXMatrixOrthoRH
D3DXMatrixOrthoOffCenterLH or D3DXMatrixOrthoOffCenterRH
D3DXMatrixPerspectiveFovLH or D3DXMatrixPerspectiveFovRH
D3DXMatrixPerspectiveLH or D3DXMatrixPerspectiveRH
D3DXMatrixPerspectiveOffCenterLH or D3DXMatrixPerspectiveOffCenterRH

(From this page)

hth
Jack

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I seem to recall one system was (historically) used in physics while the other was used in mathematics...or something like that.

As to why microsoft did it, here's a couple of possible good reasons:
1) RenderMan uses a left-hand coordinate system
2) Left hand systems are often used for cameras and camera placement (the uvn camera system is left handed)

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As you can see, the difference between left-handed and right-handed is pretty minimal. To convert a vector between the two, just reverse the sign of the Z axis. You must also reverse the triangle winding order if you are dealing with a set of polygons.

It's not a big deal, really.

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You can use D3DX in order to transform your view to righthand. ITs really easy.

My engine uses DX and uses right handed coords so it is friendly to 3DStudioMax so programmers and artists we can all talk in the same coords.

Luck!
Guimo

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You can definately use either system in mathematics, we switch between them all the time depending on who is lecturing. However, I seem to remember one of my old mechanics tutors telling me that the cross product was only properly rigoursly defined in a right handed coordinate system. Although it makes no difference when you are programming really :)

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Original post by weasalmongler
You can definately use either system in mathematics, we switch between them all the time depending on who is lecturing. However, I seem to remember one of my old mechanics tutors telling me that the cross product was only properly rigoursly defined in a right handed coordinate system. Although it makes no difference when you are programming really :)

I don't see that being possible. Since it's possible to map all elements of the LHCS to corresponding elements of the RHCS, if the dot product was undefined in LHCS, then it would be undefined in RHCS.

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Original post by Oluseyi
I say your education is deficient.

deficient???
I know it can be tranformed to each other.
But what I wanna know is why they let us know that, it is quite simple though.

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Quote:
Original post by Coder
I seem to recall one system was (historically) used in physics while the other was used in mathematics...or something like that.

I think that's wrong. I was taught both physics, mathematics and even opengl, all use right-hand coordinate, only but direct X

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Quote:
Original post by creavol
Quote:
Original post by Oluseyi
I say your education is deficient.

deficient???
I know it can be tranformed to each other.
But what I wanna know is why they let us know that, it is quite simple though.


[If you are asking for the definition, "deficient" means that something is lacking (not enough education in this case).]

Because there are built in functions to convert between the two in case you prefer one over the other, this shouldn't be a problem. [smile]

Edit: Microsoft is cool, there is no need for "M$".

[Edited by - Daniel Miller on August 1, 2005 11:05:28 AM]

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We mathematicians use whatever coordinate systems we want, including non-orthogonal ones!

For the current argument, it make not difference whatsoever. Right-Handed or Left-Handed is a matter of representation, not algebra. Just like the Y pointing down in screen coordinates... its like saying mathematicians use apples instead of oranges to count.

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It really isn't a big deal... you can actually use whatever coordinate system you want in either API, at least if you're using vertex shaders rather than the FF pipeline. I've written apps that use LH, RH, z-up, and a million other variants in both OpenGL and Direct3D... as for the reasons, there are several for each decision. Math tends to use RHS (although one can use either), but historically a lot of computer graphics stuff has used LHS. Thus I contend that both are valid choices...

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What I never liked about OGL's right hand system was that an identity view matrix has the camera pointing down -z. It's weird. It means that if you use vector-orientation representation, then you can't put those vectors directly into the matrix (the Z will end up backwards from what you expect). A vertical Z axis ends up making a lot more sense, which is why I transitioned recently. You can put vectors directly into the matrix -- all that changes is that the Look vector slides into the y column, and the Up vector slides into the z column. But this way, when you start with all positive coefficients, you end with a system that is all positive. And when I'm doing physics or math, I usually prefer vertical Z as well.

As for D3D, it allows you to switch handedness rather easily, so it doesn't really matter in the end.


(P.S. Don't say "M$". It's a good indication of an immature and idiotic person.)

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Quote:
Original post by Daniel Miller
Edit: Microsoft is cool, there is no need for "M$".


Quote:

Yeah, and it is MS and not M$.


Quote:

(P.S. Don't say "M$". It's a good indication of an immature and idiotic person.)


Apparently, you all have deficient 1337ness educations. Anyone kewl hates M$ for being the oppressive fascist regime that it truly is. Heaven forbid they give us the world's best 3D API and dare to make it in...LEFT-HANDED COORDINATES!



And for good measure:
M$

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Quote:
Original post by creavol
deficient???
Yes, deficient. An adequate education will have taught you that coordinate systems are abstract modes of representation, that the same point or path/spline can be represented in cartesian/rectilinear, curvilinear/cylindrical and spherical systems, and that some problems are more easily solved in alternate coordinate systems. Having learned that, and knowing that the left-handed system evolved because of the desire to extend the inverted-Y 2D system of screen space, you should long ago have concluded that the handedness of a coordinate system was immaterial.

Don't get mad. I was an engineering major before I switched to the liberal arts.

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Anyone kewl hates M$ for being the oppressive fascist regime that it truly is.


w0rd. l1nux tru3ly 15 4 500p33r330r 05. M$ CAN BURN !!!!!!DIE BILL GATES !!!!!!!! l1nux 43

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Quote:
Original post by Drakex
Quote:
Anyone kewl hates M$ for being the oppressive fascist regime that it truly is.


w0rd. l1nux tru3ly 15 4 500p33r330r 05. M$ CAN BURN !!!!!!DIE BILL GATES !!!!!!!! l1nux 43


I am ashamed that I can understand that...

Anyways, you have to understand that both systems work the same. If you feel more comfortable with the forward z being negative, by all means, use a right handed system. Hell, you can make <.543264, .384646, .746265> be the up vextor. It really doesn't matter. All of the above are perfectly valid. just use whichever you feel comfortable with.

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i have a question, if left hand and right hand coordinate systems r wat was inthe picture above. what coordinate system is 3Ds Max working in?! it flipps the Y and Z, and chnage the sign of the Z, not only 3DS Max, but GTK Radiant as well.

why do they do that? wats the point of it?

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      m_pContext->CommitShaderResources(m_pSRB, COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES); The method takes a pointer to the shader resource binding object and makes all resources the object holds available for the shaders. In the case of D3D12, this only requires setting appropriate descriptor tables in the command list. For older APIs, this typically requires setting all resources individually.
      Next-generation APIs require the application to track the state of every resource and explicitly inform the system about all state transitions. For instance, if a texture was used as render target before, while the next draw command is going to use it as shader resource, a transition barrier needs to be executed. Diligent Engine does the heavy lifting of state tracking.  When CommitShaderResources() method is called with COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES flag, the engine commits and transitions resources to correct states at the same time. Note that transitioning resources does introduce some overhead. The engine tracks state of every resource and it will not issue the barrier if the state is already correct. But checking resource state is an overhead that can sometimes be avoided. The engine provides IDeviceContext::TransitionShaderResources() method that only transitions resources:
      m_pContext->TransitionShaderResources(m_pPSO, m_pSRB); In some scenarios it is more efficient to transition resources once and then only commit them.
      Invoking Draw Command
      The final step is to set states that are not part of the PSO, such as render targets, vertex and index buffers. Diligent Engine uses Direct3D11-syle API that is translated to other native API calls under the hood:
      ITextureView *pRTVs[] = {m_pRTV}; m_pContext->SetRenderTargets(_countof( pRTVs ), pRTVs, m_pDSV); // Clear render target and depth buffer const float zero[4] = {0, 0, 0, 0}; m_pContext->ClearRenderTarget(nullptr, zero); m_pContext->ClearDepthStencil(nullptr, CLEAR_DEPTH_FLAG, 1.f); // Set vertex and index buffers IBuffer *buffer[] = {m_pVertexBuffer}; Uint32 offsets[] = {0}; Uint32 strides[] = {sizeof(MyVertex)}; m_pContext->SetVertexBuffers(0, 1, buffer, strides, offsets, SET_VERTEX_BUFFERS_FLAG_RESET); m_pContext->SetIndexBuffer(m_pIndexBuffer, 0); Different native APIs use various set of function to execute draw commands depending on command details (if the command is indexed, instanced or both, what offsets in the source buffers are used etc.). For instance, there are 5 draw commands in Direct3D11 and more than 9 commands in OpenGL with something like glDrawElementsInstancedBaseVertexBaseInstance not uncommon. Diligent Engine hides all details with single IDeviceContext::Draw() method that takes takes DrawAttribs structure as an argument. The structure members define all attributes required to perform the command (primitive topology, number of vertices or indices, if draw call is indexed or not, if draw call is instanced or not, if draw call is indirect or not, etc.). For example:
      DrawAttribs attrs; attrs.IsIndexed = true; attrs.IndexType = VT_UINT16; attrs.NumIndices = 36; attrs.Topology = PRIMITIVE_TOPOLOGY_TRIANGLE_LIST; pContext->Draw(attrs); For compute commands, there is IDeviceContext::DispatchCompute() method that takes DispatchComputeAttribs structure that defines compute grid dimension.
      Source Code
      Full engine source code is available on GitHub and is free to use. The repository contains tutorials, sample applications, asteroids performance benchmark and an example Unity project that uses Diligent Engine in native plugin.
      Atmospheric scattering sample demonstrates how Diligent Engine can be used to implement various rendering tasks: loading textures from files, using complex shaders, rendering to multiple render targets, using compute shaders and unordered access views, etc.

      Asteroids performance benchmark is based on this demo developed by Intel. It renders 50,000 unique textured asteroids and allows comparing performance of Direct3D11 and Direct3D12 implementations. Every asteroid is a combination of one of 1000 unique meshes and one of 10 unique textures.

      Finally, there is an example project that shows how Diligent Engine can be integrated with Unity.

      Future Work
      The engine is under active development. It currently supports Windows desktop, Universal Windows, Linux, Android, MacOS, and iOS platforms. Direct3D11, Direct3D12, OpenGL/GLES backends are now feature complete. Vulkan backend is coming next, and Metal backend is in the plan.
    • By LifeArtist
      Good Evening,
      I want to make a 2D game which involves displaying some debug information. Especially for collision, enemy sights and so on ...
      First of I was thinking about all those shapes which I need will need for debugging purposes: circles, rectangles, lines, polygons.
      I am really stucked right now because of the fundamental question:
      Where do I store my vertices positions for each line (object)? Currently I am not using a model matrix because I am using orthographic projection and set the final position within the VBO. That means that if I add a new line I would have to expand the "points" array and re-upload (recall glBufferData) it every time. The other method would be to use a model matrix and a fixed vbo for a line but it would be also messy to exactly create a line from (0,0) to (100,20) calculating the rotation and scale to make it fit.
      If I proceed with option 1 "updating the array each frame" I was thinking of having 4 draw calls every frame for the lines vao, polygons vao and so on. 
      In addition to that I am planning to use some sort of ECS based architecture. So the other question would be:
      Should I treat those debug objects as entities/components?
      For me it would make sense to treat them as entities but that's creates a new issue with the previous array approach because it would have for example a transform and render component. A special render component for debug objects (no texture etc) ... For me the transform component is also just a matrix but how would I then define a line?
      Treating them as components would'nt be a good idea in my eyes because then I would always need an entity. Well entity is just an id !? So maybe its a component?
      Regards,
      LifeArtist
    • By QQemka
      Hello. I am coding a small thingy in my spare time. All i want to achieve is to load a heightmap (as the lowest possible walking terrain), some static meshes (elements of the environment) and a dynamic character (meaning i can move, collide with heightmap/static meshes and hold a varying item in a hand ). Got a bunch of questions, or rather problems i can't find solution to myself. Nearly all are deal with graphics/gpu, not the coding part. My c++ is on high enough level.
      Let's go:
      Heightmap - i obviously want it to be textured, size is hardcoded to 256x256 squares. I can't have one huge texture stretched over entire terrain cause every pixel would be enormous. Thats why i decided to use 2 specified textures. First will be a tileset consisting of 16 square tiles (u v range from 0 to 0.25 for first tile and so on) and second a 256x256 buffer with 0-15 value representing index of the tile from tileset for every heigtmap square. Problem is, how do i blend the edges nicely and make some computationally cheap changes so its not obvious there are only 16 tiles? Is it possible to generate such terrain with some existing program?
      Collisions - i want to use bounding sphere and aabb. But should i store them for a model or entity instance? Meaning i have 20 same trees spawned using the same tree model, but every entity got its own transformation (position, scale etc). Storing collision component per instance grats faster access + is precalculated and transformed (takes additional memory, but who cares?), so i stick with this, right? What should i do if object is dynamically rotated? The aabb is no longer aligned and calculating per vertex min/max everytime object rotates/scales is pretty expensive, right?
      Drawing aabb - problem similar to above (storing aabb data per instance or model). This time in my opinion per model is enough since every instance also does not have own vertex buffer but uses the shared one (so 20 trees share reference to one tree model). So rendering aabb is about taking the model's aabb, transforming with instance matrix and voila. What about aabb vertex buffer (this is more of a cosmetic question, just curious, bumped onto it in time of writing this). Is it better to make it as 8 points and index buffer (12 lines), or only 2 vertices with min/max x/y/z and having the shaders dynamically generate 6 other vertices and draw the box? Or maybe there should be just ONE 1x1x1 cube box template moved/scaled per entity?
      What if one model got a diffuse texture and a normal map, and other has only diffuse? Should i pass some bool flag to shader with that info, or just assume that my game supports only diffuse maps without fancy stuff?
      There were several more but i forgot/solved them at time of writing
      Thanks in advance
    • By RenanRR
      Hi All,
      I'm reading the tutorials from learnOpengl site (nice site) and I'm having a question on the camera (https://learnopengl.com/Getting-started/Camera).
      I always saw the camera being manipulated with the lookat, but in tutorial I saw the camera being changed through the MVP arrays, which do not seem to be camera, but rather the scene that changes:
      Vertex Shader:
      #version 330 core layout (location = 0) in vec3 aPos; layout (location = 1) in vec2 aTexCoord; out vec2 TexCoord; uniform mat4 model; uniform mat4 view; uniform mat4 projection; void main() { gl_Position = projection * view * model * vec4(aPos, 1.0f); TexCoord = vec2(aTexCoord.x, aTexCoord.y); } then, the matrix manipulated:
      ..... glm::mat4 projection = glm::perspective(glm::radians(fov), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f); ourShader.setMat4("projection", projection); .... glm::mat4 view = glm::lookAt(cameraPos, cameraPos + cameraFront, cameraUp); ourShader.setMat4("view", view); .... model = glm::rotate(model, glm::radians(angle), glm::vec3(1.0f, 0.3f, 0.5f)); ourShader.setMat4("model", model);  
      So, some doubts:
      - Why use it like that?
      - Is it okay to manipulate the camera that way?
      -in this way, are not the vertex's positions that changes instead of the camera?
      - I need to pass MVP to all shaders of object in my scenes ?
       
      What it seems, is that the camera stands still and the scenery that changes...
      it's right?
       
       
      Thank you
       
    • By dpadam450
      Sampling a floating point texture where the alpha channel holds 4-bytes of packed data into the float. I don't know how to cast the raw memory to treat it as an integer so I can perform bit-shifting operations.

      int rgbValue = int(textureSample.w);//4 bytes of data packed as color
      // algorithm might not be correct and endianness might need switching.
      vec3 extractedData = vec3(  rgbValue & 0xFF000000,  (rgbValue << 8) & 0xFF000000, (rgbValue << 16) & 0xFF000000);
      extractedData /= 255.0f;
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