From 72a54bce2f4140ef0429c43e8ce0e4008aef975e Mon Sep 17 00:00:00 2001
From: bjorn <tie.372@gmail.com>
Date: Tue, 23 Feb 2021 12:07:16 -0700
Subject: [PATCH] Support STL models;

Only binary STL files are supported right now, ASCII is more challenging.
---
 src/modules/data/modelData.c     |  2 +
 src/modules/data/modelData.h     |  1 +
 src/modules/data/modelData_stl.c | 76 ++++++++++++++++++++++++++++++++
 src/modules/graphics/model.c     |  3 +-
 4 files changed, 81 insertions(+), 1 deletion(-)
 create mode 100644 src/modules/data/modelData_stl.c

diff --git a/src/modules/data/modelData.c b/src/modules/data/modelData.c
index de69454d..32b5e230 100644
--- a/src/modules/data/modelData.c
+++ b/src/modules/data/modelData.c
@@ -12,6 +12,8 @@ ModelData* lovrModelDataCreate(Blob* source, ModelDataIO* io) {
     return model;
   } else if (lovrModelDataInitObj(model, source, io)) {
     return model;
+  } else if (lovrModelDataInitStl(model, source, io)) {
+    return model;
   }
 
   lovrThrow("Unable to load model from '%s'", source->name);
diff --git a/src/modules/data/modelData.h b/src/modules/data/modelData.h
index 89741fb1..778f0bec 100644
--- a/src/modules/data/modelData.h
+++ b/src/modules/data/modelData.h
@@ -221,5 +221,6 @@ typedef void* ModelDataIO(const char* filename, size_t* bytesRead);
 ModelData* lovrModelDataCreate(struct Blob* blob, ModelDataIO* io);
 ModelData* lovrModelDataInitGltf(ModelData* model, struct Blob* blob, ModelDataIO* io);
 ModelData* lovrModelDataInitObj(ModelData* model, struct Blob* blob, ModelDataIO* io);
+ModelData* lovrModelDataInitStl(ModelData* model, struct Blob* blob, ModelDataIO* io);
 void lovrModelDataDestroy(void* ref);
 void lovrModelDataAllocate(ModelData* model);
diff --git a/src/modules/data/modelData_stl.c b/src/modules/data/modelData_stl.c
new file mode 100644
index 00000000..adb166bd
--- /dev/null
+++ b/src/modules/data/modelData_stl.c
@@ -0,0 +1,76 @@
+#include "data/modelData.h"
+#include "data/blob.h"
+#include "core/maf.h"
+#include "core/util.h"
+#include <stdlib.h>
+#include <string.h>
+
+static ModelData* lovrModelDataInitStlAscii(ModelData* model, Blob* source, ModelDataIO* io) {
+  lovrThrow("ASCII STL files are not supported yet");
+  return NULL;
+}
+
+// The binary format has an 80 byte header, followed by a u32 triangle count, followed by 50 byte
+// triangles.  Each triangle has a vec3 normal, 3 vec3 vertices, and 2 bytes of padding.
+extern ModelData* lovrModelDataInitStlBinary(ModelData* model, Blob* source, ModelDataIO* io, uint32_t triangleCount) {
+  char* data = (char*) source->data + 84;
+
+  uint32_t vertexCount = triangleCount * 3;
+  size_t vertexBufferSize = vertexCount * 6 * sizeof(float);
+  float* vertices = malloc(vertexBufferSize);
+  lovrAssert(vertices, "Out of memory");
+
+  model->blobCount = 1;
+  model->bufferCount = 1;
+  model->attributeCount = 2;
+  model->primitiveCount = 1;
+  model->nodeCount = 1;
+
+  lovrModelDataAllocate(model);
+
+  model->blobs[0] = lovrBlobCreate(vertices, vertexBufferSize, "stl vertex data");
+  model->buffers[0] = (ModelBuffer) { .data = (char*) vertices, .size = vertexBufferSize, .stride = 6 * sizeof(float) };
+  model->attributes[0] = (ModelAttribute) { .count = vertexCount, .components = 3, .type = F32, .offset = 0 * sizeof(float) };
+  model->attributes[1] = (ModelAttribute) { .count = vertexCount, .components = 3, .type = F32, .offset = 3 * sizeof(float) };
+  model->primitives[0] = (ModelPrimitive) {
+    .mode = DRAW_TRIANGLES,
+    .material = ~0u,
+    .attributes = {
+      [ATTR_POSITION] = &model->attributes[0],
+      [ATTR_NORMAL] = &model->attributes[1]
+    }
+  };
+  model->nodes[0] = (ModelNode) {
+    .matrix = true,
+    .transform.matrix = MAT4_IDENTITY,
+    .primitiveCount = 1,
+    .skin = ~0u
+  };
+
+  for (uint32_t i = 0; i < triangleCount; i++) {
+    memcpy(vertices + 3, data, 12);
+    memcpy(vertices + 9, data, 12);
+    memcpy(vertices + 15, data, 12), data += 12;
+    memcpy(vertices + 0, data, 12), data += 12;
+    memcpy(vertices + 6, data, 12), data += 12;
+    memcpy(vertices + 12, data, 12), data += 12;
+    vertices += 18;
+    data += 2;
+  }
+
+  return model;
+}
+
+ModelData* lovrModelDataInitStl(ModelData* model, Blob* source, ModelDataIO* io) {
+  if (source->size > strlen("solid ") && !memcmp(source->data, "solid ", strlen("solid "))) {
+    return lovrModelDataInitStlAscii(model, source, io);
+  } else if (source->size > 84) {
+    uint32_t triangleCount;
+    memcpy(&triangleCount, (char*) source->data + 80, sizeof(triangleCount));
+    if (source->size == 84 + 50 * triangleCount) {
+      return lovrModelDataInitStlBinary(model, source, io, triangleCount);
+    }
+  }
+
+  return NULL;
+}
diff --git a/src/modules/graphics/model.c b/src/modules/graphics/model.c
index 1686b17f..b3764817 100644
--- a/src/modules/graphics/model.c
+++ b/src/modules/graphics/model.c
@@ -130,7 +130,8 @@ Model* lovrModelCreate(ModelData* data) {
     model->meshes = calloc(data->primitiveCount, sizeof(Mesh*));
     for (uint32_t i = 0; i < data->primitiveCount; i++) {
       ModelPrimitive* primitive = &data->primitives[i];
-      model->meshes[i] = lovrMeshCreate(primitive->mode, NULL, 0);
+      uint32_t vertexCount = primitive->attributes[ATTR_POSITION] ? primitive->attributes[ATTR_POSITION]->count : 0;
+      model->meshes[i] = lovrMeshCreate(primitive->mode, NULL, vertexCount);
 
       if (primitive->material != ~0u) {
         lovrMeshSetMaterial(model->meshes[i], model->materials[primitive->material]);