os/graphics/m3g/m3gcore11/src/m3g_indexbuffer.c
changeset 0 bde4ae8d615e
     1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/os/graphics/m3g/m3gcore11/src/m3g_indexbuffer.c	Fri Jun 15 03:10:57 2012 +0200
     1.3 @@ -0,0 +1,555 @@
     1.4 +/*
     1.5 +* Copyright (c) 2003 Nokia Corporation and/or its subsidiary(-ies).
     1.6 +* All rights reserved.
     1.7 +* This component and the accompanying materials are made available
     1.8 +* under the terms of the License "Eclipse Public License v1.0"
     1.9 +* which accompanies this distribution, and is available
    1.10 +* at the URL "http://www.eclipse.org/legal/epl-v10.html".
    1.11 +*
    1.12 +* Initial Contributors:
    1.13 +* Nokia Corporation - initial contribution.
    1.14 +*
    1.15 +* Contributors:
    1.16 +*
    1.17 +* Description: IndexBuffer implementation
    1.18 +*
    1.19 +*/
    1.20 +
    1.21 +
    1.22 +/*!
    1.23 + * \internal
    1.24 + * \file
    1.25 + * \brief IndexBuffer implementation
    1.26 + */
    1.27 +
    1.28 +#ifndef M3G_CORE_INCLUDE
    1.29 +#   error included by m3g_core.c; do not compile separately.
    1.30 +#endif
    1.31 +
    1.32 +#include "m3g_indexbuffer.h"
    1.33 +
    1.34 +/*----------------------------------------------------------------------
    1.35 + * Private functions
    1.36 + *--------------------------------------------------------------------*/
    1.37 +
    1.38 +
    1.39 +/*----------------------------------------------------------------------
    1.40 + * Internal functions
    1.41 + *--------------------------------------------------------------------*/
    1.42 +
    1.43 +/*!
    1.44 + * \internal
    1.45 + * \brief IndexBuffer destructor
    1.46 + *
    1.47 + * \param obj IndexBuffer object
    1.48 + */
    1.49 +static void m3gDestroyIndexBuffer(Object *obj)
    1.50 +{
    1.51 +    IndexBuffer *ib = (IndexBuffer *) obj;
    1.52 +    M3G_VALIDATE_OBJECT(ib);
    1.53 +
    1.54 +	{
    1.55 +		Interface *m3g = M3G_INTERFACE(ib);
    1.56 +		m3gFree(m3g, ib->indices);
    1.57 +		m3gFree(m3g, ib->lengths);
    1.58 +	}
    1.59 +
    1.60 +    m3gDestroyObject(obj);
    1.61 +}
    1.62 +
    1.63 +/*!
    1.64 + * \internal
    1.65 + * \brief Sends the contents of an IndexBuffer to the current GL
    1.66 + * instance for processing
    1.67 + *
    1.68 + * \param buf IndexBuffer object
    1.69 + */
    1.70 +static void m3gSendIndexBuffer(const IndexBuffer *buf)
    1.71 +{
    1.72 +    M3G_VALIDATE_OBJECT(buf);
    1.73 +    
    1.74 +    M3G_ASSERT(buf->indices);
    1.75 +    M3G_ASSERT(buf->glPrimitive == GL_TRIANGLE_STRIP);
    1.76 +    
    1.77 +    M3G_BEGIN_PROFILE(M3G_INTERFACE(buf), M3G_PROFILE_NGL_DRAW);
    1.78 +    glDrawElements(buf->glPrimitive, buf->indexCount, buf->glType, buf->indices);
    1.79 +    M3G_END_PROFILE(M3G_INTERFACE(buf), M3G_PROFILE_NGL_DRAW);
    1.80 +
    1.81 +    M3G_ASSERT_GL;
    1.82 +}
    1.83 +
    1.84 +/*!
    1.85 + * \internal
    1.86 + * \brief Gets triangle indices, used by mesh pick routine.
    1.87 + *
    1.88 + * \param buf IndexBuffer object
    1.89 + * \param triangle triangle index
    1.90 + * \param indices triangle indices
    1.91 + * \retval M3G_TRUE  indices fetched
    1.92 + * \retval M3G_FALSE no such triangle
    1.93 + */
    1.94 +static M3Gbool m3gGetIndices(const IndexBuffer *buf,
    1.95 +                             M3Gint triangle,
    1.96 +                             M3Gint *indices) {
    1.97 +    M3Gubyte *bptr;
    1.98 +    M3Gushort *sptr;
    1.99 +
   1.100 +    if(triangle + 2 >= buf->indexCount) return M3G_FALSE;
   1.101 +
   1.102 +    switch(buf->glType) {
   1.103 +        case GL_UNSIGNED_BYTE:
   1.104 +            bptr = (M3Gubyte *)buf->indices;
   1.105 +            bptr += triangle;
   1.106 +            indices[0] = *bptr++;
   1.107 +            indices[1] = *bptr++;
   1.108 +            indices[2] = *bptr;
   1.109 +            break;
   1.110 +
   1.111 +        case GL_UNSIGNED_SHORT:
   1.112 +            sptr = (M3Gushort *)buf->indices;
   1.113 +            sptr += triangle;
   1.114 +            indices[0] = (M3Gint) *sptr++;
   1.115 +            indices[1] = (M3Gint) *sptr++;
   1.116 +            indices[2] = (M3Gint) *sptr;
   1.117 +            break;
   1.118 +    }
   1.119 +
   1.120 +    /* Winding */
   1.121 +    indices[3] = triangle & 1;
   1.122 +
   1.123 +    return M3G_TRUE;
   1.124 +}
   1.125 +
   1.126 +/*!
   1.127 + * \internal
   1.128 + * \brief Overloaded Object3D method.
   1.129 + *
   1.130 + * \param originalObj original IndexBuffer object
   1.131 + * \param cloneObj pointer to cloned IndexBuffer object
   1.132 + * \param pairs array for all object-duplicate pairs
   1.133 + * \param numPairs number of pairs
   1.134 + */
   1.135 +static M3Gbool m3gIndexBufferDuplicate(const Object *originalObj,
   1.136 +                                       Object **cloneObj,
   1.137 +                                       Object **pairs,
   1.138 +                                       M3Gint *numPairs)
   1.139 +{
   1.140 +    M3Gint size;
   1.141 +    IndexBuffer *original = (IndexBuffer *)originalObj;
   1.142 +    IndexBuffer *clone = (IndexBuffer *)m3gAllocZ(originalObj->interface, sizeof(IndexBuffer));
   1.143 +
   1.144 +    if (clone == NULL) {
   1.145 +        return M3G_FALSE;
   1.146 +    }
   1.147 +
   1.148 +    *cloneObj = (Object *)clone;
   1.149 +
   1.150 +    /* Call init since this object is 'manually' created */
   1.151 +    m3gInitObject((Object*) clone, originalObj->interface, M3G_CLASS_INDEX_BUFFER);
   1.152 +
   1.153 +    if(!m3gObjectDuplicate(originalObj, cloneObj, pairs, numPairs)) {
   1.154 +        return M3G_FALSE;
   1.155 +    }
   1.156 +
   1.157 +    clone->indexCount = original->indexCount;
   1.158 +    clone->glType = original->glType;
   1.159 +    clone->glPrimitive = original->glPrimitive;
   1.160 +    clone->stripCount = original->stripCount;
   1.161 +
   1.162 +    if (clone->glType == GL_UNSIGNED_BYTE) {
   1.163 +        size = clone->indexCount;
   1.164 +        clone->indices = m3gAlloc(originalObj->interface, size);
   1.165 +    }
   1.166 +    else {
   1.167 +        size = clone->indexCount * sizeof(M3Gshort);
   1.168 +        clone->indices = m3gAlloc(originalObj->interface, size);
   1.169 +    }
   1.170 +
   1.171 +    clone->lengths = (M3Gushort *) m3gAlloc(originalObj->interface, (M3Gsize) clone->stripCount*2);
   1.172 +
   1.173 +    if(clone->indices == NULL || clone->lengths == NULL) {
   1.174 +        /* Duplicate will call m3gDeleteObject */
   1.175 +        return M3G_FALSE;
   1.176 +    }
   1.177 +
   1.178 +    m3gCopy(clone->lengths, original->lengths, clone->stripCount*2);
   1.179 +    m3gCopy(clone->indices, original->indices, size);
   1.180 +
   1.181 +    return M3G_TRUE;
   1.182 +}
   1.183 +
   1.184 +/*!
   1.185 + * \internal
   1.186 + * \brief Gets maximum index of this index buffer.
   1.187 + *
   1.188 + * \param buf IndexBuffer object
   1.189 + * \return maximum index used
   1.190 + */
   1.191 +static M3Gint m3gGetMaxIndex(const IndexBuffer *buf)
   1.192 +{
   1.193 +    return buf->maxIndex;
   1.194 +}
   1.195 +
   1.196 +/*----------------------------------------------------------------------
   1.197 + * Virtual function table
   1.198 + *--------------------------------------------------------------------*/
   1.199 +
   1.200 +static const ObjectVFTable m3gvf_IndexBuffer = {
   1.201 +    m3gObjectApplyAnimation,
   1.202 +    m3gObjectIsCompatible,
   1.203 +    m3gObjectUpdateProperty,
   1.204 +    m3gObjectDoGetReferences,
   1.205 +    m3gObjectFindID,
   1.206 +    m3gIndexBufferDuplicate,
   1.207 +    m3gDestroyIndexBuffer
   1.208 +};
   1.209 +
   1.210 +/*----------------------------------------------------------------------
   1.211 + * Public functions
   1.212 + *--------------------------------------------------------------------*/
   1.213 +
   1.214 +/*!
   1.215 + * \brief Creates an implicit strip buffer
   1.216 + *
   1.217 + * \param interface     M3G interface
   1.218 + * \param stripCount    number of triangle strips
   1.219 + * \param stripLengths  array of strip lengths
   1.220 + * \param firstIndex    first index
   1.221 + * \retval IndexBuffer new IndexBuffer object
   1.222 + * \retval NULL IndexBuffer creating failed
   1.223 + */
   1.224 +M3G_API M3GIndexBuffer m3gCreateImplicitStripBuffer(
   1.225 +    M3GInterface interface,
   1.226 +    M3Gsizei stripCount,
   1.227 +    const M3Gsizei *stripLengths,
   1.228 +    M3Gint firstIndex)
   1.229 +{
   1.230 +	M3GIndexBuffer ib;
   1.231 +	M3Gint *stripIndices, i, indexCount = 0;
   1.232 +    Interface *m3g = (Interface *) interface;
   1.233 +    M3G_VALIDATE_INTERFACE(m3g);
   1.234 +	
   1.235 +	if (stripLengths == NULL) {
   1.236 +		m3gRaiseError(m3g, M3G_NULL_POINTER);
   1.237 +        return 0;
   1.238 +	}
   1.239 +
   1.240 +    if (stripCount == 0) {
   1.241 +		m3gRaiseError(m3g, M3G_INVALID_VALUE);
   1.242 +        return 0;
   1.243 +    }
   1.244 +
   1.245 +	for (i = 0; i < stripCount; i++) {
   1.246 +		if(stripLengths[i] < 3) {
   1.247 +			m3gRaiseError(m3g, M3G_INVALID_VALUE);
   1.248 +            return 0;
   1.249 +		}
   1.250 +		indexCount += stripLengths[i];
   1.251 +	}
   1.252 +
   1.253 +	if (firstIndex < 0 ||
   1.254 +		(firstIndex + indexCount) > 65535) {
   1.255 +		m3gRaiseError(m3g, M3G_INVALID_INDEX);
   1.256 +        return 0;
   1.257 +	}
   1.258 +
   1.259 +	stripIndices = m3gAlloc(m3g, indexCount * sizeof(M3Gint));
   1.260 +
   1.261 +	if (stripIndices == NULL) {
   1.262 +		return 0;	/* automatic out of memory from m3gAlloc */
   1.263 +	}
   1.264 +
   1.265 +	/* Generate explict arrays */
   1.266 +    
   1.267 +	for (i = 0; i < indexCount; i++) {
   1.268 +		stripIndices[i] = firstIndex + i;
   1.269 +	}
   1.270 +
   1.271 +	ib = m3gCreateStripBuffer(interface,
   1.272 +                              M3G_TRIANGLE_STRIPS,
   1.273 +                              stripCount, stripLengths,
   1.274 +                              M3G_INT, indexCount, stripIndices);
   1.275 +	m3gFree(m3g, stripIndices);
   1.276 +	return ib;
   1.277 +}
   1.278 +
   1.279 +/*!
   1.280 + * \brief Creates an indexed triangle strip buffer
   1.281 + *
   1.282 + * \note Optimizes rendering by joining the indices. Also scans the
   1.283 + * array for the maximum value, and allocates the storage using the
   1.284 + * smallest possible data type.
   1.285 + *
   1.286 + * \param interface     M3G interface
   1.287 + * \param primitive     primitive type, always M3G_TRIANGLE_STRIPS
   1.288 + * \param stripCount    number of triangle strips
   1.289 + * \param stripLengths  array of strip lengths
   1.290 + * \param type          data type of indices
   1.291 + * \param numIndices    number of indices
   1.292 + * \param stripIndices  array of indices
   1.293 + * \retval IndexBuffer new IndexBuffer object
   1.294 + * \retval NULL IndexBuffer creating failed
   1.295 + */
   1.296 +M3G_API M3GIndexBuffer m3gCreateStripBuffer(M3GInterface interface,
   1.297 +                                            M3Gprimitive primitive,
   1.298 +                                            M3Gsizei stripCount,
   1.299 +                                            const M3Gsizei *stripLengths,
   1.300 +                                            M3Gdatatype type,
   1.301 +                                            M3Gsizei numIndices,
   1.302 +                                            const void *stripIndices)
   1.303 +{
   1.304 +    M3Gsizei joinedIndexCount = 0;
   1.305 +    M3Gsizei originalIndexCount = 0;
   1.306 +    M3Gint maxIndex = 0;
   1.307 +
   1.308 +    Interface *m3g = (Interface *) interface;
   1.309 +    M3G_VALIDATE_INTERFACE(m3g);
   1.310 +
   1.311 +    if (primitive != M3G_TRIANGLE_STRIPS
   1.312 +        || (type != M3G_INT && type != M3G_UINT)) {
   1.313 +        m3gRaiseError(m3g, M3G_INVALID_ENUM);
   1.314 +        return 0;
   1.315 +    }
   1.316 +    if (stripIndices == NULL ||
   1.317 +    	stripLengths == NULL) {
   1.318 +        m3gRaiseError(m3g, M3G_NULL_POINTER);
   1.319 +        return 0;
   1.320 +    }
   1.321 +
   1.322 +	if (stripCount == 0 || numIndices == 0) {
   1.323 +        m3gRaiseError(m3g, M3G_INVALID_VALUE);
   1.324 +        return 0;
   1.325 +	}
   1.326 +
   1.327 +	{
   1.328 +        /* Find the maximum index and count the actual number of indices
   1.329 +         * required for joining the strips */
   1.330 +        
   1.331 +        int strip;
   1.332 +        M3Gint *idx = (M3Gint *) stripIndices;
   1.333 +        for (strip = 0; strip < stripCount; ++strip) {
   1.334 +            if(stripLengths[strip] < 3) {
   1.335 +                m3gRaiseError(m3g, M3G_INVALID_VALUE);
   1.336 +                return 0;
   1.337 +            }
   1.338 +            if (strip != 0) {
   1.339 +                joinedIndexCount += (M3Guint)((joinedIndexCount & 1) ? 3 : 2);
   1.340 +            }
   1.341 +
   1.342 +            joinedIndexCount += (M3Guint) stripLengths[strip];
   1.343 +            originalIndexCount += (M3Guint) stripLengths[strip];
   1.344 +
   1.345 +        	if (numIndices < originalIndexCount) {
   1.346 +        		m3gRaiseError(m3g, M3G_INVALID_VALUE);
   1.347 +                return 0;
   1.348 +        	}
   1.349 +
   1.350 +            M3G_ASSERT(stripLengths[strip] > 0);
   1.351 +            {
   1.352 +                int i;
   1.353 +                for (i = 0; i < stripLengths[strip]; ++i, ++idx) {
   1.354 +                    if ((*idx & 0xFFFF0000u) != 0) { /* > 65535? */
   1.355 +                    	m3gRaiseError(m3g, M3G_INVALID_INDEX);
   1.356 +                        return 0;
   1.357 +                    }
   1.358 +                    if (*idx > maxIndex)
   1.359 +                        maxIndex = *idx;
   1.360 +                }
   1.361 +            }
   1.362 +        }
   1.363 +    }
   1.364 +
   1.365 +    {
   1.366 +        /* Allocate the buffer object */
   1.367 +    
   1.368 +        IndexBuffer *buf = m3gAllocZ(m3g, sizeof(IndexBuffer));
   1.369 +        if (buf == NULL) {
   1.370 +            return 0;
   1.371 +        }
   1.372 +		/* IndexBuffer is derived from Object */
   1.373 +		m3gInitObject(&buf->object, m3g, M3G_CLASS_INDEX_BUFFER);
   1.374 +
   1.375 +        buf->glPrimitive = GL_TRIANGLE_STRIP;
   1.376 +        buf->indexCount = joinedIndexCount;
   1.377 +
   1.378 +        /* Allocate the index elements as either bytes or shorts,
   1.379 +         * depending on the maximum value we need to store. Note that
   1.380 +         * OpenGL ES does not support 32-bit indices */
   1.381 +        
   1.382 +        if (maxIndex <= 0xFF) {
   1.383 +            buf->indices = m3gAlloc(m3g, (M3Gsize) joinedIndexCount);
   1.384 +            buf->glType = GL_UNSIGNED_BYTE;
   1.385 +        }
   1.386 +        else {
   1.387 +            M3G_ASSERT(maxIndex <= 0xFFFF);
   1.388 +            buf->indices = m3gAlloc(m3g, (M3Gsize) joinedIndexCount*2);
   1.389 +            buf->glType = GL_UNSIGNED_SHORT;
   1.390 +        }
   1.391 +        
   1.392 +        /* Allocate space for original strip lengths */
   1.393 +        buf->lengths = (M3Gushort *) m3gAlloc(m3g, (M3Gsize) stripCount*2);
   1.394 +
   1.395 +        if (buf->indices == NULL || buf->lengths == NULL) {
   1.396 +            m3gDeleteObject((M3GObject) buf);
   1.397 +            return 0;
   1.398 +        }
   1.399 +
   1.400 +        buf->stripCount = stripCount;
   1.401 +
   1.402 +        {
   1.403 +            /* Copy the indices, converting to the chosen type and
   1.404 +             * joining the strips as we go */
   1.405 +            
   1.406 +            M3Guint *src = (M3Guint*) stripIndices;     /* type asserted above */
   1.407 +            void *dstStrip = buf->indices;
   1.408 +            int strip;
   1.409 +            
   1.410 +            for (strip = 0; strip < stripCount; ++strip) {
   1.411 +                int i;
   1.412 +
   1.413 +                buf->lengths[strip] = (M3Gushort) stripLengths[strip];
   1.414 +
   1.415 +                /*@notfunction@*/
   1.416 +                #define COPY_STRIP(indexType) do {              \
   1.417 +                    indexType *dst = (indexType *) dstStrip;    \
   1.418 +                    if (strip != 0) {                           \
   1.419 +                        *dst++ = (indexType) *(src-1);          \
   1.420 +                        *dst++ = (indexType) *src;              \
   1.421 +                        if (stripLengths[strip-1] & 1) {        \
   1.422 +                            *dst++ = (indexType) *src;          \
   1.423 +                        }                                       \
   1.424 +                    }                                           \
   1.425 +                    for (i = 0; i < stripLengths[strip]; ++i) { \
   1.426 +                        *dst++ = (indexType) *src++;            \
   1.427 +                    }                                           \
   1.428 +                    dstStrip = (void *) dst;                    \
   1.429 +                    M3G_ASSERT(dst <= (indexType *)(buf->indices) + buf->indexCount); \
   1.430 +                } while (0)
   1.431 +                    
   1.432 +                switch (buf->glType) {
   1.433 +                    
   1.434 +                case GL_UNSIGNED_BYTE:
   1.435 +                    COPY_STRIP(GLubyte);
   1.436 +                    break;
   1.437 +                    
   1.438 +                case GL_UNSIGNED_SHORT:
   1.439 +                    COPY_STRIP(GLushort);
   1.440 +                    break;
   1.441 +                    
   1.442 +                default:
   1.443 +                    M3G_ASSERT(0);
   1.444 +                }
   1.445 +                
   1.446 +                #undef COPY_STRIP
   1.447 +            }
   1.448 +        }
   1.449 +
   1.450 +        /* Store maximum index */
   1.451 +        buf->maxIndex = maxIndex;
   1.452 +
   1.453 +        /* All done! */
   1.454 +        return (M3GIndexBuffer) buf;
   1.455 +    }
   1.456 +}
   1.457 +
   1.458 +/*!
   1.459 + * \brief Gets the number of index batches in an index buffer
   1.460 + *
   1.461 + * An index batch usually corresponds to a single OpenGL rendering
   1.462 + * call.
   1.463 + *
   1.464 + * \param buffer  index buffer handle
   1.465 + * \return number of rendering batches
   1.466 + */
   1.467 +M3G_API M3Gint m3gGetBatchCount(M3GIndexBuffer buffer)
   1.468 +{
   1.469 +    M3G_VALIDATE_OBJECT(buffer);
   1.470 +    M3G_UNREF(buffer);
   1.471 +    return 1;
   1.472 +}
   1.473 +
   1.474 +/*!
   1.475 + * \brief Returns the indices in an index batch
   1.476 + *
   1.477 + * \param buffer      index buffer handle
   1.478 + * \param batchIndex  batch index
   1.479 + * \param indices     pointer to a buffer to hold the indices
   1.480 + * \retval M3G_TRUE   buffer has explicit indices
   1.481 + * \retval M3G_FALSE  buffer has implicit indices; only the first index
   1.482 + *                    is stored in \c indices
   1.483 + */
   1.484 +M3G_API M3Gbool m3gGetBatchIndices(M3GIndexBuffer buffer,
   1.485 +                                   M3Gint batchIndex,
   1.486 +                                   M3Gint *indices)
   1.487 +{
   1.488 +    M3Gint i, j, tri = 0;
   1.489 +    M3Gint triIndices[4] = {0, 0, 0, 0};
   1.490 +    M3G_VALIDATE_OBJECT(buffer);
   1.491 +    M3G_UNREF(batchIndex);
   1.492 +
   1.493 +    for (i = 0; i < buffer->stripCount; i++) {
   1.494 +        for (j = 0; j < buffer->lengths[i] - 2; j++) {
   1.495 +            m3gGetIndices(buffer, tri, triIndices); 
   1.496 +
   1.497 +            *indices++ = triIndices[0];
   1.498 +            if (triIndices[3] == 0) {
   1.499 +                *indices++ = triIndices[1];
   1.500 +                *indices++ = triIndices[2];
   1.501 +            }
   1.502 +            else {
   1.503 +                *indices++ = triIndices[2];
   1.504 +                *indices++ = triIndices[1];
   1.505 +            }
   1.506 +
   1.507 +            ++tri;
   1.508 +        }
   1.509 +
   1.510 +        /* Eliminate degenerate triangles */
   1.511 +        if (buffer->lengths[i] & 1) {
   1.512 +            tri += 5;
   1.513 +        }
   1.514 +        else {
   1.515 +            tri += 4;
   1.516 +        }
   1.517 +    }
   1.518 +
   1.519 +    return M3G_TRUE;
   1.520 +}
   1.521 +
   1.522 +/*!
   1.523 + * \brief Returns the size of an index batch
   1.524 + *
   1.525 + * \param buffer      index buffer handle
   1.526 + * \param batchIndex  batch index
   1.527 + * \return number of indices in the batch
   1.528 + */
   1.529 +M3G_API M3Gint m3gGetBatchSize(M3GIndexBuffer buffer, M3Gint batchIndex)
   1.530 +{
   1.531 +    M3Gint i, count = 0;
   1.532 +    M3G_VALIDATE_OBJECT(buffer);
   1.533 +    
   1.534 +    if (batchIndex != 0) {
   1.535 +        return 0;
   1.536 +    }
   1.537 +
   1.538 +    for (i = 0; i < buffer->stripCount; i++) {
   1.539 +        count += buffer->lengths[i] - 2;
   1.540 +    }
   1.541 +
   1.542 +    return count * 3;
   1.543 +}
   1.544 +
   1.545 +/*!
   1.546 + * \brief Returns the primitive type of an index buffer
   1.547 + *
   1.548 + * \param buffer  index buffer handle
   1.549 + * \return type of primitives stored in the buffer
   1.550 + */
   1.551 +M3G_API M3Gprimitive m3gGetPrimitive(M3GIndexBuffer buffer)
   1.552 +{
   1.553 +    M3G_UNREF(buffer);
   1.554 +    M3G_VALIDATE_OBJECT(buffer);
   1.555 +    M3G_ASSERT(buffer->glPrimitive == GL_TRIANGLE_STRIP);
   1.556 +    return M3G_TRIANGLE_STRIPS;
   1.557 +}
   1.558 +