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Fix IdxBuffer related comments. (#4845, #4863)

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This commit is contained in:
ocornut 2022-01-05 12:15:58 +01:00
parent 28eabcb099
commit 04bc0b0bb8
2 changed files with 16 additions and 11 deletions
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19
imgui.cpp
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@ -295,6 +295,7 @@ CODE
// TODO: Setup viewport covering draw_data->DisplayPos to draw_data->DisplayPos + draw_data->DisplaySize
// TODO: Setup orthographic projection matrix cover draw_data->DisplayPos to draw_data->DisplayPos + draw_data->DisplaySize
// TODO: Setup shader: vertex { float2 pos, float2 uv, u32 color }, fragment shader sample color from 1 texture, multiply by vertex color.
ImVec2 clip_off = draw_data->DisplayPos;
for (int n = 0; n < draw_data->CmdListsCount; n++)
{
const ImDrawList* cmd_list = draw_data->CmdLists[n];
@ -309,9 +310,11 @@ CODE
}
else
{
// The texture for the draw call is specified by pcmd->GetTexID().
// The vast majority of draw calls will use the Dear ImGui texture atlas, which value you have set yourself during initialization.
MyEngineBindTexture((MyTexture*)pcmd->GetTexID());
// Project scissor/clipping rectangles into framebuffer space
ImVec2 clip_min(pcmd->ClipRect.x - clip_off.x, pcmd->ClipRect.y - clip_off.y);
ImVec2 clip_max(pcmd->ClipRect.z - clip_off.x, pcmd->ClipRect.w - clip_off.y);
if (clip_max.x <= clip_min.x || clip_max.y <= clip_min.y)
continue;
// We are using scissoring to clip some objects. All low-level graphics API should support it.
// - If your engine doesn't support scissoring yet, you may ignore this at first. You will get some small glitches
@ -322,14 +325,16 @@ CODE
// - In the interest of supporting multi-viewport applications (see 'docking' branch on github),
// always subtract draw_data->DisplayPos from clipping bounds to convert them to your viewport space.
// - Note that pcmd->ClipRect contains Min+Max bounds. Some graphics API may use Min+Max, other may use Min+Size (size being Max-Min)
ImVec2 pos = draw_data->DisplayPos;
MyEngineScissor((int)(pcmd->ClipRect.x - pos.x), (int)(pcmd->ClipRect.y - pos.y), (int)(pcmd->ClipRect.z - pos.x), (int)(pcmd->ClipRect.w - pos.y));
MyEngineSetScissor(clip_min.x, clip_min.y, clip_max.x, clip_max.y);
// The texture for the draw call is specified by pcmd->GetTexID().
// The vast majority of draw calls will use the Dear ImGui texture atlas, which value you have set yourself during initialization.
MyEngineBindTexture((MyTexture*)pcmd->GetTexID());
// Render 'pcmd->ElemCount/3' indexed triangles.
// By default the indices ImDrawIdx are 16-bit, you can change them to 32-bit in imconfig.h if your engine doesn't support 16-bit indices.
MyEngineDrawIndexedTriangles(pcmd->ElemCount, sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT, idx_buffer, vtx_buffer);
MyEngineDrawIndexedTriangles(pcmd->ElemCount, sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT, idx_buffer + pcmd->IdxOffset, vtx_buffer, pcmd->VtxOffset);
}
idx_buffer += pcmd->ElemCount;
}
}
}

8
imgui.h
View File

@ -2278,16 +2278,16 @@ typedef void (*ImDrawCallback)(const ImDrawList* parent_list, const ImDrawCmd* c
#define ImDrawCallback_ResetRenderState (ImDrawCallback)(-1)
// Typically, 1 command = 1 GPU draw call (unless command is a callback)
// - VtxOffset/IdxOffset: When 'io.BackendFlags & ImGuiBackendFlags_RendererHasVtxOffset' is enabled,
// those fields allow us to render meshes larger than 64K vertices while keeping 16-bit indices.
// Pre-1.71 backends will typically ignore the VtxOffset/IdxOffset fields.
// - VtxOffset: When 'io.BackendFlags & ImGuiBackendFlags_RendererHasVtxOffset' is enabled,
// this fields allow us to render meshes larger than 64K vertices while keeping 16-bit indices.
// Backends made for <1.71. will typically ignore the VtxOffset fields.
// - The ClipRect/TextureId/VtxOffset fields must be contiguous as we memcmp() them together (this is asserted for).
struct ImDrawCmd
{
ImVec4 ClipRect; // 4*4 // Clipping rectangle (x1, y1, x2, y2). Subtract ImDrawData->DisplayPos to get clipping rectangle in "viewport" coordinates
ImTextureID TextureId; // 4-8 // User-provided texture ID. Set by user in ImfontAtlas::SetTexID() for fonts or passed to Image*() functions. Ignore if never using images or multiple fonts atlas.
unsigned int VtxOffset; // 4 // Start offset in vertex buffer. ImGuiBackendFlags_RendererHasVtxOffset: always 0, otherwise may be >0 to support meshes larger than 64K vertices with 16-bit indices.
unsigned int IdxOffset; // 4 // Start offset in index buffer. Always equal to sum of ElemCount drawn so far.
unsigned int IdxOffset; // 4 // Start offset in index buffer.
unsigned int ElemCount; // 4 // Number of indices (multiple of 3) to be rendered as triangles. Vertices are stored in the callee ImDrawList's vtx_buffer[] array, indices in idx_buffer[].
ImDrawCallback UserCallback; // 4-8 // If != NULL, call the function instead of rendering the vertices. clip_rect and texture_id will be set normally.
void* UserCallbackData; // 4-8 // The draw callback code can access this.