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OpenGL Buildings in 3D game

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I've began to learn 3D game programming with OpenGL not long ago so I'm new to all this. I've done a lot of stuff in 2D so the concepts are familiar to me but I have some thoughts about how to do some things. I'm at the phase now where I got an more or less empty world up and runing and the ability to move around in it. What I'd like to o is work a little more on the world and add some objects like buildings, trees, benches, etc. What I'm wondering is how should I implement this? Should I use 3D models for the objects oronly for the smaller ones like benches and use big Texture images on a flat polygon for the buildings? The buildings aren't supposed to be interactable, just for the view. Also, I'm more into the gameplay creation so what are the recommendations for the models? I'd like to spend as little time as possible coding loaders and such. Thanx

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If you're a designer then don't do any complicated graphic work.

Ask a graphist to build you nice objects, and/or a programmer to help you intergrating one of the numerous libs to import 3ds for example.

What kind of game are you building ? As a designer, have you a concept or are you "just filling a world with benches" ?

If you have a nice game concept, you know as a designer that "filling" the world can come at the very end of the project. You can play using white boxes for houses and quads for benches if the gameplay is good !

Peous

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I wouldn't call myself a designer, it's the programming I'm interested in. I only meant that I'm into the designing programming, so to speak. I don't mind programming everything, including graphics, it's just that I'm not very familiar with different model types and to be honest I don't want to learn about how .3ds works so I can program a loader.

Also, I'm not just filling the world with objects, I was only asking what techniques are recommended for this when the time comes. The buildings and benches were simply two examples. For instance, I'm asking how can I put a building in my world with as much effective code as possible. The building won't play a central role in the game so the only restriction is that it looks somewhat decent. I myself thought of just using a box with textures on and normal mapping. But like I said, I'm still new to all this so that's why I thought I could ask what other, more experienced people think.

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Guest Anonymous Poster
hi.

i would suggest you read up about it. (the capital words are important)
for far away objects as well as sky and horizon, you should read up about SKYBOXes.
for placing objects that appear very often, you could use BILLBOARDS. (like grass, etc.)
and you will maybe create a SCENEGRAPH for your world where the objects are placed and can be culled by the renderer.
for real 3d-objects you can use MIPMAPPING and terrain algorithms like GEOMORPHING.

and maybe later on you will have some DECALS and/or PARTICLE SYSTEMS and use some advanced techniques like SKELETAL ANIMATION.

there are always libs for loading models and such, when you use directx i would recommend using *.x - files, because these are easy to implement and supported by the d3dx-functions. later on, you can change this and support more model-formats.

so make your way to your first small game world, thats more than many others are able to do. good luck.

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download my game here
www.3drock.co.uk

It does exactly what you're saying - the buildings are basically quads - but you'd be surprised at how good they look. I took about 300 fotos of shops and appartments in my home town.

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Whatever you want it's your stuff, only limits are your imagination.

It's easy to create content in a 3D graphics program such as Lightwave, Maya, DelEd, Gamespace, or Milkshape, there's usually plenty of free models and textures you can use at your disposal to accomplish the simple texturing task.

Then on the coding end you'd handle the loading and rendering of the 3D content, it's good to go with a standard model format that's supported by alot of 3D graphics editing tools so you can easily import/export content too and from graphics editing environments for further editing and/or authoring.

A standard such as DirectX or OBJ/3DS is common, all geometry based file formats store data needed related to the geometry, you simply need to read this data then store it in an object like a mesh object vclass you define to store the information about the meshes geometry, then display it when the time comes, optionally you can create a tool and your own proprietary format to organize things the way you want and add further functionality not included in the normal format.

This method pay's off in the long run because once you get the basic coding of the loader, display, and other things you want added, the rest of your focus becomes on content creation and interaction programming, here's a list of file formats to help you get started: http://local.wasp.uwa.edu.au/~pbourke/dataformats

Here's an example of a simple box using the OBJ geometry file format:
# Vertices: 8
# Points: 0
# Lines: 0
# Faces: 6
# Materials: 1

o 1

# Vertex list

v -0.5 -0.5 0.5
v -0.5 -0.5 -0.5
v -0.5 0.5 -0.5
v -0.5 0.5 0.5
v 0.5 -0.5 0.5
v 0.5 -0.5 -0.5
v 0.5 0.5 -0.5
v 0.5 0.5 0.5

# Point/Line/Face list

usemtl Default
f 4 3 2 1
f 2 6 5 1
f 3 7 6 2
f 8 7 3 4
f 5 8 4 1
f 6 7 8 5

# End of file

Once you know how to already display simple geometry and just read data into your program via a simple text stream, you can even just use a windows control such as RichEditTextBox to load the file as a plain text file it's really not all that hard to do and the longterm effects are generally worth it. The only challenge comes in handling files where a specific tool modifies the original output in a way extra and unneeded data isn't require. Such as:

#This file was created by: A specific tool blah blah blahhhh. Created year: Blah blah blahhhh.

The concept is simple, the above part of the file says you have 8 vertices, so once you locate the first vertice/vertex defined by the line which contains the first lowercase v as the first charactor, you'd do a count loop of 8 lines, for each line you read in a new Vector3 eg X,Y,Z which respresents the 3D points of your geometry to be drawn to the screen. The the material list defines a total of 6 faces, this also contains your proper vertice/vertex drawing order, and there's 1 mesh material defined which is applied to the entire mesh on all faces of the mesh, that's it. If you want to just focus on the geometry you can handle loading and application of textures and shaders seperate from the file format, meaning you can ignore the material and texture data and other complicated stuff in the file and just setup your own material texture settings that are seperate, even resave this to your own file format for reloading later, that way the geometry would be loaded via the OBJ file, then when comes time to load the material and/or texture information can do that from a seperate file dedicated to that information.

Like this:
Graphics engine loading mesh geometry Box.obj....
Graphics engine loading and applying material and texture data to geometry Box.mt....
And so on...

You can also create a simple small editor for 3D geometry object placement and store object position, rotation, scale, and other settings such as special graphics engine render and display settings, as well as basic object interactivity and animation keyframe and/or other things.

The simpler the design and effort of your graphics engine, and the more flexible and re-usable the overall design architecture, even with standard software applications, the quicker things get done, less headaches in the longrun, and more you can focus on more complicated tasks such as physics detail, AI, and hardware optimizations, etc...

[Edited by - Knight Chat X on September 28, 2006 7:04:54 PM]

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      The next step is to bind all required shader resources to the GPU pipeline, which is accomplished by IDeviceContext::CommitShaderResources() method:
      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 two samples, asteroids performance benchmark and example Unity project that uses Diligent Engine in native plugin.
      AntTweakBar sample is Diligent Engine’s “Hello World” example.

       
      Atmospheric scattering sample is a more advanced example. It 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 and Android platforms. Direct3D11, Direct3D12, OpenGL/GLES backends are now feature complete. Vulkan backend is coming next, and support for more platforms is planned.
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